[Micronaut] Generating and downloading files as ZIP or JSON

0566

Intro

In this time, I will try generating and downloading files as ZIP.
If any error occurs during generation, generate and download a JSON file.

Generating a ZIP archive

First, I will load a CSV file and split it into multiple CSV files.

FileController.java 

<span>package</span> <span>jp.masanori</span><span>;</span>
<span>import</span> <span>io.micronaut.http.annotation.Controller</span><span>;</span>
<span>import</span> <span>io.micronaut.http.annotation.Get</span><span>;</span>
<span>import</span> <span>io.micronaut.http.HttpResponse</span><span>;</span>
<span>import</span> <span>io.micronaut.http.server.types.files.SystemFile</span><span>;</span>
<span>@Controller</span><span>(</span><span>"/files"</span><span>)</span>
<span>public</span> <span>class</span> <span>FileController</span> <span>{</span>
    <span>private</span> <span>final</span> <span>ResultCsvGenerator</span> <span>csvGen</span><span>;</span>
    <span>public</span> <span>FileController</span><span>(</span><span>ResultCsvGenerator</span> <span>csvGen</span><span>)</span> <span>{</span>
        <span>this</span><span>.</span><span>csvGen</span> <span>=</span> <span>csvGen</span><span>;</span>
    <span>}</span>    
    <span>@Get</span><span>(</span><span>uri</span><span>=</span><span>"zip"</span><span>)</span>
    <span>public</span> <span>HttpResponse</span><span><</span><span>SystemFile</span><span>></span> <span>getZip</span><span>()</span> <span>{</span>
        <span>SystemFile</span> <span>result</span> <span>=</span> <span>csvGen</span><span>.</span><span>generate</span><span>();</span>
        <span>return</span> <span>HttpResponse</span><span>.</span><span>ok</span><span>(</span><span>result</span><span>)</span>
            <span>.</span><span>contentType</span><span>(</span><span>"application/zip"</span><span>);</span>
    <span>}</span>
<span>}</span>
<span>package</span> <span>jp.masanori</span><span>;</span>

<span>import</span> <span>io.micronaut.http.annotation.Controller</span><span>;</span>
<span>import</span> <span>io.micronaut.http.annotation.Get</span><span>;</span>
<span>import</span> <span>io.micronaut.http.HttpResponse</span><span>;</span>
<span>import</span> <span>io.micronaut.http.server.types.files.SystemFile</span><span>;</span>

<span>@Controller</span><span>(</span><span>"/files"</span><span>)</span>
<span>public</span> <span>class</span> <span>FileController</span> <span>{</span>
    <span>private</span> <span>final</span> <span>ResultCsvGenerator</span> <span>csvGen</span><span>;</span>
    <span>public</span> <span>FileController</span><span>(</span><span>ResultCsvGenerator</span> <span>csvGen</span><span>)</span> <span>{</span>
        <span>this</span><span>.</span><span>csvGen</span> <span>=</span> <span>csvGen</span><span>;</span>
    <span>}</span>    
    <span>@Get</span><span>(</span><span>uri</span><span>=</span><span>"zip"</span><span>)</span>
    <span>public</span> <span>HttpResponse</span><span><</span><span>SystemFile</span><span>></span> <span>getZip</span><span>()</span> <span>{</span>
        <span>SystemFile</span> <span>result</span> <span>=</span> <span>csvGen</span><span>.</span><span>generate</span><span>();</span>
        <span>return</span> <span>HttpResponse</span><span>.</span><span>ok</span><span>(</span><span>result</span><span>)</span>
            <span>.</span><span>contentType</span><span>(</span><span>"application/zip"</span><span>);</span>
    <span>}</span>
<span>}</span>
package jp.masanori;

import io.micronaut.http.annotation.Controller;
import io.micronaut.http.annotation.Get;
import io.micronaut.http.HttpResponse;
import io.micronaut.http.server.types.files.SystemFile;

@Controller("/files")
public class FileController {
    private final ResultCsvGenerator csvGen;
    public FileController(ResultCsvGenerator csvGen) {
        this.csvGen = csvGen;
    }    
    @Get(uri="zip")
    public HttpResponse<SystemFile> getZip() {
        SystemFile result = csvGen.generate();
        return HttpResponse.ok(result)
            .contentType("application/zip");
    }
}

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sample.csv 

--12345678
Content-Disposition: mixed; name="sample"; filename="sample.csv";
Content-Type: text/csv
id,名前,メッセージ,タグ
0,サンプル,こんにちは,debug
1,サンプル2,世界,world
2,サンプル3,こんばんは,debug
3,サンプル4,おはよう,morning
--abcdefgh
Content-Disposition: mixed; name="example"; filename="サンプル.csv";
Content-Type: text/csv
id,名前,メッセージ,タグ
4,サンプル,こんにちは,debug
5,サンプル2,世界,world
6,サンプル3,こんばんは,debug
7,サンプル4,おはよう,morning
--12345678
Content-Disposition: mixed; name="sample"; filename="sample.csv";
Content-Type: text/csv
id,名前,メッセージ,タグ
0,サンプル,こんにちは,debug
1,サンプル2,世界,world
2,サンプル3,こんばんは,debug
3,サンプル4,おはよう,morning

--abcdefgh
Content-Disposition: mixed; name="example"; filename="サンプル.csv";
Content-Type: text/csv
id,名前,メッセージ,タグ
4,サンプル,こんにちは,debug
5,サンプル2,世界,world
6,サンプル3,こんばんは,debug
7,サンプル4,おはよう,morning
--12345678
Content-Disposition: mixed; name="sample"; filename="sample.csv";
Content-Type: text/csv
id,名前,メッセージ,タグ
0,サンプル,こんにちは,debug
1,サンプル2,世界,world
2,サンプル3,こんばんは,debug
3,サンプル4,おはよう,morning

--abcdefgh
Content-Disposition: mixed; name="example"; filename="サンプル.csv";
Content-Type: text/csv
id,名前,メッセージ,タグ
4,サンプル,こんにちは,debug
5,サンプル2,世界,world
6,サンプル3,こんばんは,debug
7,サンプル4,おはよう,morning

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ResultCsvGenerator.java 

<span>package</span> <span>jp.masanori</span><span>;</span>
<span>import</span> <span>java.io.BufferedOutputStream</span><span>;</span>
<span>import</span> <span>java.io.File</span><span>;</span>
<span>import</span> <span>java.io.FileOutputStream</span><span>;</span>
<span>import</span> <span>java.io.IOException</span><span>;</span>
<span>import</span> <span>java.nio.file.Files</span><span>;</span>
<span>import</span> <span>java.nio.file.Paths</span><span>;</span>
<span>import</span> <span>java.util.ArrayList</span><span>;</span>
<span>import</span> <span>java.util.HashMap</span><span>;</span>
<span>import</span> <span>java.util.List</span><span>;</span>
<span>import</span> <span>java.util.Map</span><span>;</span>
<span>import</span> <span>java.util.regex.Matcher</span><span>;</span>
<span>import</span> <span>java.util.regex.Pattern</span><span>;</span>
<span>import</span> <span>java.util.zip.ZipEntry</span><span>;</span>
<span>import</span> <span>java.util.zip.ZipOutputStream</span><span>;</span>
<span>import</span> <span>org.slf4j.Logger</span><span>;</span>
<span>import</span> <span>org.slf4j.LoggerFactory</span><span>;</span>
<span>import</span> <span>io.micronaut.http.server.types.files.SystemFile</span><span>;</span>
<span>import</span> <span>jakarta.inject.Singleton</span><span>;</span>
<span>import</span> <span>jp.masanori.dto.ResultCsv</span><span>;</span>
<span>@Singleton</span>
<span>public</span> <span>class</span> <span>ResultCsvGenerator</span> <span>{</span>
    <span>private</span> <span>final</span> <span>Logger</span> <span>logger</span><span>;</span>
    <span>private</span> <span>final</span> <span>Pattern</span> <span>cdPattern</span><span>;</span>
    <span>private</span> <span>final</span> <span>Pattern</span> <span>beiPattern</span><span>;</span>
    <span>public</span> <span>ResultCsvGenerator</span><span>()</span> <span>{</span>
        <span>this</span><span>.</span><span>logger</span> <span>=</span> <span>LoggerFactory</span><span>.</span><span>getLogger</span><span>(</span><span>ResultCsvGenerator</span><span>.</span><span>class</span><span>);</span>
        <span>this</span><span>.</span><span>cdPattern</span> <span>=</span> <span>Pattern</span><span>.</span><span>compile</span><span>(</span><span>"(Content-Disposition).+(filename=)\"(.+)\""</span><span>);</span>
    <span>}</span>
    <span>public</span> <span>SystemFile</span> <span>generate</span><span>()</span> <span>{</span>
        <span>try</span> <span>{</span>
            <span>byte</span><span>[]</span> <span>fileData</span> <span>=</span> <span>Files</span>
                <span>.</span><span>readAllBytes</span><span>(</span><span>Paths</span><span>.</span><span>get</span><span>(</span><span>"C:/Users/example/sample.csv"</span><span>));</span>
            <span>List</span><span><</span><span>ResultCsv</span><span>></span> <span>csvValues</span> <span>=</span> <span>new</span> <span>ArrayList</span><span><>();</span>
            <span>String</span> <span>name</span> <span>=</span> <span>""</span><span>;</span>
            <span>String</span> <span>value</span> <span>=</span> <span>""</span><span>;</span>
            <span>String</span><span>[]</span> <span>splitted</span> <span>=</span> <span>new</span> <span>String</span><span>(</span><span>fileData</span><span>,</span> <span>"SJIS"</span><span>).</span><span>split</span><span>(</span><span>"\n"</span><span>);</span>
            <span>for</span> <span>(</span><span>int</span> <span>i</span> <span>=</span> <span>0</span><span>;</span> <span>i</span> <span><</span> <span>splitted</span><span>.</span><span>length</span><span>;</span> <span>i</span><span>++)</span> <span>{</span>
                <span>// split the value by "--"</span>
                <span>if</span> <span>(</span><span>splitted</span><span>[</span><span>i</span><span>].</span><span>startsWith</span><span>(</span><span>"--"</span><span>))</span> <span>{</span>
                    <span>if</span> <span>(</span><span>name</span><span>.</span><span>length</span><span>()</span> <span><=</span> <span>0</span><span>)</span> <span>{</span>
                        <span>continue</span><span>;</span>
                    <span>}</span>
                    <span>ResultCsv</span> <span>result</span> <span>=</span> <span>new</span> <span>ResultCsv</span><span>(</span><span>name</span><span>,</span> <span>value</span><span>);</span>
                    <span>csvValues</span><span>.</span><span>add</span><span>(</span><span>result</span><span>);</span>
                    <span>name</span> <span>=</span> <span>""</span><span>;</span>
                    <span>value</span> <span>=</span> <span>""</span><span>;</span>
                    <span>continue</span><span>;</span>
                <span>}</span>
                <span>// get file names from "Content-Disposition" rows</span>
                <span>Matcher</span> <span>cdMatcher</span> <span>=</span> <span>cdPattern</span><span>.</span><span>matcher</span><span>(</span><span>splitted</span><span>[</span><span>i</span><span>]);</span>
                <span>if</span> <span>(</span><span>cdMatcher</span><span>.</span><span>find</span><span>())</span> <span>{</span>
                    <span>name</span> <span>=</span> <span>cdMatcher</span><span>.</span><span>group</span><span>(</span><span>cdMatcher</span><span>.</span><span>groupCount</span><span>());</span>
                    <span>continue</span><span>;</span>
                <span>}</span>
                <span>// skip "Content-Type" rows</span>
                <span>if</span> <span>(</span><span>splitted</span><span>[</span><span>i</span><span>].</span><span>startsWith</span><span>(</span><span>"Content-Type"</span><span>))</span> <span>{</span>
                    <span>continue</span><span>;</span>
                <span>}</span>
                <span>// add other rows as values</span>
                <span>if</span> <span>(</span><span>name</span><span>.</span><span>length</span><span>()</span> <span>></span> <span>0</span><span>)</span> <span>{</span>
                    <span>value</span> <span>+=</span> <span>splitted</span><span>[</span><span>i</span><span>];</span>
                    <span>value</span> <span>+=</span> <span>"\n"</span><span>;</span>
                <span>}</span>
            <span>}</span>
            <span>if</span><span>(</span><span>name</span><span>.</span><span>length</span><span>()</span> <span>></span> <span>0</span><span>)</span> <span>{</span>
                <span>ResultCsv</span> <span>result</span> <span>=</span> <span>new</span> <span>ResultCsv</span><span>(</span><span>name</span><span>,</span> <span>value</span><span>);</span>
                <span>csvValues</span><span>.</span><span>add</span><span>(</span><span>result</span><span>);</span>
            <span>}</span>
            <span>return</span> <span>generateZipFile</span><span>(</span><span>csvValues</span><span>);</span>
        <span>}</span> <span>catch</span><span>(</span><span>IOException</span> <span>ex</span><span>)</span> <span>{</span>
            <span>logger</span><span>.</span><span>error</span><span>(</span><span>"Failed generating a ZIP file"</span><span>,</span> <span>ex</span><span>);</span>
            <span>return</span> <span>null</span><span>;</span>
        <span>}</span>
    <span>}</span>
    <span>private</span> <span>SystemFile</span> <span>generateZipFile</span><span>(</span><span>List</span><span><</span><span>ResultCsv</span><span>></span> <span>values</span><span>)</span> <span>throws</span> <span>IOException</span> <span>{</span>
        <span>File</span> <span>tmpFile</span> <span>=</span> <span>File</span><span>.</span><span>createTempFile</span><span>(</span><span>"result"</span><span>,</span> <span>"zip"</span><span>);</span>
        <span>try</span> <span>(</span><span>ZipOutputStream</span> <span>zip</span> <span>=</span> <span>new</span> <span>ZipOutputStream</span><span>(</span><span>new</span> <span>BufferedOutputStream</span><span>(</span>
                <span>new</span> <span>FileOutputStream</span><span>(</span><span>tmpFile</span><span>))))</span> <span>{</span>
            <span>for</span> <span>(</span><span>ResultCsv</span> <span>csv</span> <span>:</span> <span>values</span><span>)</span> <span>{</span>
                <span>// add CSV files into ZIP archive</span>
                <span>String</span> <span>fileName</span> <span>=</span> <span>csv</span><span>.</span><span>getName</span><span>();</span>
                <span>if</span> <span>(</span><span>fileName</span> <span>==</span> <span>null</span><span>)</span> <span>{</span>
                    <span>continue</span><span>;</span>
                <span>}</span>
                <span>zip</span><span>.</span><span>putNextEntry</span><span>(</span><span>new</span> <span>ZipEntry</span><span>(</span><span>fileName</span><span>));</span>
                <span>byte</span><span>[]</span> <span>value</span> <span>=</span> <span>csv</span><span>.</span><span>getValue</span><span>().</span><span>getBytes</span><span>(</span><span>"SJIS"</span><span>);</span>
                <span>zip</span><span>.</span><span>write</span><span>(</span><span>value</span><span>,</span> <span>0</span><span>,</span> <span>value</span><span>.</span><span>length</span><span>);</span>
            <span>}</span>
        <span>}</span>
        <span>// set ZIP file name</span>
        <span>return</span> <span>new</span> <span>SystemFile</span><span>(</span><span>tmpFile</span><span>).</span><span>attach</span><span>(</span><span>"result.zip"</span><span>);</span>
    <span>}</span>
<span>}</span>
<span>package</span> <span>jp.masanori</span><span>;</span>

<span>import</span> <span>java.io.BufferedOutputStream</span><span>;</span>
<span>import</span> <span>java.io.File</span><span>;</span>
<span>import</span> <span>java.io.FileOutputStream</span><span>;</span>
<span>import</span> <span>java.io.IOException</span><span>;</span>
<span>import</span> <span>java.nio.file.Files</span><span>;</span>
<span>import</span> <span>java.nio.file.Paths</span><span>;</span>
<span>import</span> <span>java.util.ArrayList</span><span>;</span>
<span>import</span> <span>java.util.HashMap</span><span>;</span>
<span>import</span> <span>java.util.List</span><span>;</span>
<span>import</span> <span>java.util.Map</span><span>;</span>
<span>import</span> <span>java.util.regex.Matcher</span><span>;</span>
<span>import</span> <span>java.util.regex.Pattern</span><span>;</span>
<span>import</span> <span>java.util.zip.ZipEntry</span><span>;</span>
<span>import</span> <span>java.util.zip.ZipOutputStream</span><span>;</span>

<span>import</span> <span>org.slf4j.Logger</span><span>;</span>
<span>import</span> <span>org.slf4j.LoggerFactory</span><span>;</span>

<span>import</span> <span>io.micronaut.http.server.types.files.SystemFile</span><span>;</span>
<span>import</span> <span>jakarta.inject.Singleton</span><span>;</span>
<span>import</span> <span>jp.masanori.dto.ResultCsv</span><span>;</span>

<span>@Singleton</span>
<span>public</span> <span>class</span> <span>ResultCsvGenerator</span> <span>{</span>
    <span>private</span> <span>final</span> <span>Logger</span> <span>logger</span><span>;</span>
    <span>private</span> <span>final</span> <span>Pattern</span> <span>cdPattern</span><span>;</span>
    <span>private</span> <span>final</span> <span>Pattern</span> <span>beiPattern</span><span>;</span>

    <span>public</span> <span>ResultCsvGenerator</span><span>()</span> <span>{</span>
        <span>this</span><span>.</span><span>logger</span> <span>=</span> <span>LoggerFactory</span><span>.</span><span>getLogger</span><span>(</span><span>ResultCsvGenerator</span><span>.</span><span>class</span><span>);</span>
        <span>this</span><span>.</span><span>cdPattern</span> <span>=</span> <span>Pattern</span><span>.</span><span>compile</span><span>(</span><span>"(Content-Disposition).+(filename=)\"(.+)\""</span><span>);</span>
    <span>}</span>
    <span>public</span> <span>SystemFile</span> <span>generate</span><span>()</span> <span>{</span>
        <span>try</span> <span>{</span>
            <span>byte</span><span>[]</span> <span>fileData</span> <span>=</span> <span>Files</span>
                <span>.</span><span>readAllBytes</span><span>(</span><span>Paths</span><span>.</span><span>get</span><span>(</span><span>"C:/Users/example/sample.csv"</span><span>));</span>
            <span>List</span><span><</span><span>ResultCsv</span><span>></span> <span>csvValues</span> <span>=</span> <span>new</span> <span>ArrayList</span><span><>();</span>
            <span>String</span> <span>name</span> <span>=</span> <span>""</span><span>;</span>
            <span>String</span> <span>value</span> <span>=</span> <span>""</span><span>;</span>
            <span>String</span><span>[]</span> <span>splitted</span> <span>=</span> <span>new</span> <span>String</span><span>(</span><span>fileData</span><span>,</span> <span>"SJIS"</span><span>).</span><span>split</span><span>(</span><span>"\n"</span><span>);</span>
            <span>for</span> <span>(</span><span>int</span> <span>i</span> <span>=</span> <span>0</span><span>;</span> <span>i</span> <span><</span> <span>splitted</span><span>.</span><span>length</span><span>;</span> <span>i</span><span>++)</span> <span>{</span>
                <span>// split the value by "--"</span>
                <span>if</span> <span>(</span><span>splitted</span><span>[</span><span>i</span><span>].</span><span>startsWith</span><span>(</span><span>"--"</span><span>))</span> <span>{</span>
                    <span>if</span> <span>(</span><span>name</span><span>.</span><span>length</span><span>()</span> <span><=</span> <span>0</span><span>)</span> <span>{</span>
                        <span>continue</span><span>;</span>
                    <span>}</span>
                    <span>ResultCsv</span> <span>result</span> <span>=</span> <span>new</span> <span>ResultCsv</span><span>(</span><span>name</span><span>,</span> <span>value</span><span>);</span>
                    <span>csvValues</span><span>.</span><span>add</span><span>(</span><span>result</span><span>);</span>
                    <span>name</span> <span>=</span> <span>""</span><span>;</span>
                    <span>value</span> <span>=</span> <span>""</span><span>;</span>
                    <span>continue</span><span>;</span>
                <span>}</span>
                <span>// get file names from "Content-Disposition" rows</span>
                <span>Matcher</span> <span>cdMatcher</span> <span>=</span> <span>cdPattern</span><span>.</span><span>matcher</span><span>(</span><span>splitted</span><span>[</span><span>i</span><span>]);</span>
                <span>if</span> <span>(</span><span>cdMatcher</span><span>.</span><span>find</span><span>())</span> <span>{</span>
                    <span>name</span> <span>=</span> <span>cdMatcher</span><span>.</span><span>group</span><span>(</span><span>cdMatcher</span><span>.</span><span>groupCount</span><span>());</span>
                    <span>continue</span><span>;</span>
                <span>}</span>
                <span>// skip "Content-Type" rows</span>
                <span>if</span> <span>(</span><span>splitted</span><span>[</span><span>i</span><span>].</span><span>startsWith</span><span>(</span><span>"Content-Type"</span><span>))</span> <span>{</span>
                    <span>continue</span><span>;</span>
                <span>}</span>
                <span>// add other rows as values</span>
                <span>if</span> <span>(</span><span>name</span><span>.</span><span>length</span><span>()</span> <span>></span> <span>0</span><span>)</span> <span>{</span>
                    <span>value</span> <span>+=</span> <span>splitted</span><span>[</span><span>i</span><span>];</span>
                    <span>value</span> <span>+=</span> <span>"\n"</span><span>;</span>
                <span>}</span>
            <span>}</span>
            <span>if</span><span>(</span><span>name</span><span>.</span><span>length</span><span>()</span> <span>></span> <span>0</span><span>)</span> <span>{</span>
                <span>ResultCsv</span> <span>result</span> <span>=</span> <span>new</span> <span>ResultCsv</span><span>(</span><span>name</span><span>,</span> <span>value</span><span>);</span>
                <span>csvValues</span><span>.</span><span>add</span><span>(</span><span>result</span><span>);</span>
            <span>}</span>
            <span>return</span> <span>generateZipFile</span><span>(</span><span>csvValues</span><span>);</span>

        <span>}</span> <span>catch</span><span>(</span><span>IOException</span> <span>ex</span><span>)</span> <span>{</span>
            <span>logger</span><span>.</span><span>error</span><span>(</span><span>"Failed generating a ZIP file"</span><span>,</span> <span>ex</span><span>);</span>
            <span>return</span> <span>null</span><span>;</span>
        <span>}</span>
    <span>}</span>
    <span>private</span> <span>SystemFile</span> <span>generateZipFile</span><span>(</span><span>List</span><span><</span><span>ResultCsv</span><span>></span> <span>values</span><span>)</span> <span>throws</span> <span>IOException</span> <span>{</span>
        <span>File</span> <span>tmpFile</span> <span>=</span> <span>File</span><span>.</span><span>createTempFile</span><span>(</span><span>"result"</span><span>,</span> <span>"zip"</span><span>);</span>
        <span>try</span> <span>(</span><span>ZipOutputStream</span> <span>zip</span> <span>=</span> <span>new</span> <span>ZipOutputStream</span><span>(</span><span>new</span> <span>BufferedOutputStream</span><span>(</span>
                <span>new</span> <span>FileOutputStream</span><span>(</span><span>tmpFile</span><span>))))</span> <span>{</span>
            <span>for</span> <span>(</span><span>ResultCsv</span> <span>csv</span> <span>:</span> <span>values</span><span>)</span> <span>{</span>
                <span>// add CSV files into ZIP archive</span>
                <span>String</span> <span>fileName</span> <span>=</span> <span>csv</span><span>.</span><span>getName</span><span>();</span>
                <span>if</span> <span>(</span><span>fileName</span> <span>==</span> <span>null</span><span>)</span> <span>{</span>
                    <span>continue</span><span>;</span>
                <span>}</span>
                <span>zip</span><span>.</span><span>putNextEntry</span><span>(</span><span>new</span> <span>ZipEntry</span><span>(</span><span>fileName</span><span>));</span>
                <span>byte</span><span>[]</span> <span>value</span> <span>=</span> <span>csv</span><span>.</span><span>getValue</span><span>().</span><span>getBytes</span><span>(</span><span>"SJIS"</span><span>);</span>
                <span>zip</span><span>.</span><span>write</span><span>(</span><span>value</span><span>,</span> <span>0</span><span>,</span> <span>value</span><span>.</span><span>length</span><span>);</span>
            <span>}</span>
        <span>}</span>
        <span>// set ZIP file name</span>
        <span>return</span> <span>new</span> <span>SystemFile</span><span>(</span><span>tmpFile</span><span>).</span><span>attach</span><span>(</span><span>"result.zip"</span><span>);</span>
    <span>}</span>
<span>}</span>
package jp.masanori;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import io.micronaut.http.server.types.files.SystemFile;
import jakarta.inject.Singleton;
import jp.masanori.dto.ResultCsv;

@Singleton
public class ResultCsvGenerator {
    private final Logger logger;
    private final Pattern cdPattern;
    private final Pattern beiPattern;

    public ResultCsvGenerator() {
        this.logger = LoggerFactory.getLogger(ResultCsvGenerator.class);
        this.cdPattern = Pattern.compile("(Content-Disposition).+(filename=)\"(.+)\"");
    }
    public SystemFile generate() {
        try {
            byte[] fileData = Files
                .readAllBytes(Paths.get("C:/Users/example/sample.csv"));
            List<ResultCsv> csvValues = new ArrayList<>();
            String name = "";
            String value = "";
            String[] splitted = new String(fileData, "SJIS").split("\n");
            for (int i = 0; i < splitted.length; i++) {
                // split the value by "--"
                if (splitted[i].startsWith("--")) {
                    if (name.length() <= 0) {
                        continue;
                    }
                    ResultCsv result = new ResultCsv(name, value);
                    csvValues.add(result);
                    name = "";
                    value = "";
                    continue;
                }
                // get file names from "Content-Disposition" rows
                Matcher cdMatcher = cdPattern.matcher(splitted[i]);
                if (cdMatcher.find()) {
                    name = cdMatcher.group(cdMatcher.groupCount());
                    continue;
                }
                // skip "Content-Type" rows
                if (splitted[i].startsWith("Content-Type")) {
                    continue;
                }
                // add other rows as values
                if (name.length() > 0) {
                    value += splitted[i];
                    value += "\n";
                }
            }
            if(name.length() > 0) {
                ResultCsv result = new ResultCsv(name, value);
                csvValues.add(result);
            }
            return generateZipFile(csvValues);

        } catch(IOException ex) {
            logger.error("Failed generating a ZIP file", ex);
            return null;
        }
    }
    private SystemFile generateZipFile(List<ResultCsv> values) throws IOException {
        File tmpFile = File.createTempFile("result", "zip");
        try (ZipOutputStream zip = new ZipOutputStream(new BufferedOutputStream(
                new FileOutputStream(tmpFile)))) {
            for (ResultCsv csv : values) {
                // add CSV files into ZIP archive
                String fileName = csv.getName();
                if (fileName == null) {
                    continue;
                }
                zip.putNextEntry(new ZipEntry(fileName));
                byte[] value = csv.getValue().getBytes("SJIS");
                zip.write(value, 0, value.length);
            }
        }
        // set ZIP file name
        return new SystemFile(tmpFile).attach("result.zip");
    }
}

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ResultCsv.java 

<span>package</span> <span>jp.masanori.dto</span><span>;</span>
<span>public</span> <span>class</span> <span>ResultCsv</span> <span>{</span>
    <span>private</span> <span>String</span> <span>name</span><span>;</span>
    <span>private</span> <span>String</span> <span>value</span><span>;</span>
    <span>public</span> <span>String</span> <span>getName</span><span>()</span> <span>{</span>
        <span>return</span> <span>name</span><span>;</span>
    <span>}</span>
    <span>public</span> <span>String</span> <span>getValue</span><span>()</span> <span>{</span>
        <span>return</span> <span>value</span><span>;</span>
    <span>}</span>
    <span>public</span> <span>ResultCsv</span><span>(</span><span>String</span> <span>name</span><span>,</span> <span>String</span> <span>value</span><span>)</span> <span>{</span>
        <span>this</span><span>.</span><span>name</span> <span>=</span> <span>name</span><span>;</span>
        <span>this</span><span>.</span><span>value</span> <span>=</span> <span>value</span><span>;</span>
    <span>}</span>
<span>}</span>
<span>package</span> <span>jp.masanori.dto</span><span>;</span>

<span>public</span> <span>class</span> <span>ResultCsv</span> <span>{</span>
    <span>private</span> <span>String</span> <span>name</span><span>;</span>
    <span>private</span> <span>String</span> <span>value</span><span>;</span>
    <span>public</span> <span>String</span> <span>getName</span><span>()</span> <span>{</span>
        <span>return</span> <span>name</span><span>;</span>
    <span>}</span>
    <span>public</span> <span>String</span> <span>getValue</span><span>()</span> <span>{</span>
        <span>return</span> <span>value</span><span>;</span>
    <span>}</span>
    <span>public</span> <span>ResultCsv</span><span>(</span><span>String</span> <span>name</span><span>,</span> <span>String</span> <span>value</span><span>)</span> <span>{</span>
        <span>this</span><span>.</span><span>name</span> <span>=</span> <span>name</span><span>;</span>
        <span>this</span><span>.</span><span>value</span> <span>=</span> <span>value</span><span>;</span>
    <span>}</span>
<span>}</span>
package jp.masanori.dto;

public class ResultCsv {
    private String name;
    private String value;
    public String getName() {
        return name;
    }
    public String getValue() {
        return value;
    }
    public ResultCsv(String name, String value) {
        this.name = name;
        this.value = value;
    }
}

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Returning a JSON file when ZIP file generation fails 

<span>package</span> <span>jp.masanori</span><span>;</span>
<span>import</span> <span>java.io.File</span><span>;</span>
<span>import</span> <span>java.io.FileOutputStream</span><span>;</span>
<span>import</span> <span>java.io.IOException</span><span>;</span>
<span>import</span> <span>com.fasterxml.jackson.core.JsonProcessingException</span><span>;</span>
<span>import</span> <span>com.fasterxml.jackson.databind.ObjectMapper</span><span>;</span>
<span>import</span> <span>io.micronaut.http.server.types.files.SystemFile</span><span>;</span>
<span>public</span> <span>class</span> <span>ActionResult</span> <span>{</span>
    <span>private</span> <span>boolean</span> <span>succeeded</span><span>;</span>
    <span>private</span> <span>String</span> <span>errorMessage</span><span>;</span>
    <span>public</span> <span>boolean</span> <span>isSucceeded</span><span>()</span> <span>{</span>
        <span>return</span> <span>succeeded</span><span>;</span>
    <span>}</span>
    <span>public</span> <span>String</span> <span>getErrorMessage</span><span>()</span> <span>{</span>
        <span>return</span> <span>errorMessage</span><span>;</span>
    <span>}</span>
    <span>public</span> <span>static</span> <span>ActionResult</span> <span>getSucceeded</span><span>()</span> <span>{</span>
        <span>ActionResult</span> <span>result</span> <span>=</span> <span>new</span> <span>ActionResult</span><span>();</span>
        <span>result</span><span>.</span><span>succeeded</span> <span>=</span> <span>true</span><span>;</span>
        <span>return</span> <span>result</span><span>;</span>
    <span>}</span>
    <span>public</span> <span>static</span> <span>ActionResult</span> <span>getFailed</span><span>(</span><span>String</span> <span>errorMessage</span><span>)</span> <span>{</span>
        <span>ActionResult</span> <span>result</span> <span>=</span> <span>new</span> <span>ActionResult</span><span>();</span>
        <span>result</span><span>.</span><span>errorMessage</span> <span>=</span> <span>errorMessage</span><span>;</span>
        <span>return</span> <span>result</span><span>;</span>
    <span>}</span>
    <span>public</span> <span>static</span> <span>String</span> <span>getFailedJson</span><span>(</span><span>String</span> <span>errorMessage</span><span>)</span> <span>throws</span> <span>JsonProcessingException</span> <span>{</span>
        <span>ActionResult</span> <span>result</span> <span>=</span> <span>ActionResult</span><span>.</span><span>getFailed</span><span>(</span><span>errorMessage</span><span>);</span>
        <span>ObjectMapper</span> <span>mapper</span> <span>=</span> <span>new</span> <span>ObjectMapper</span><span>();</span>
        <span>return</span> <span>mapper</span><span>.</span><span>writeValueAsString</span><span>(</span><span>result</span><span>);</span>
    <span>}</span>
    <span>public</span> <span>static</span> <span>SystemFile</span> <span>getFailedJsonFile</span><span>(</span><span>String</span> <span>errorMessage</span><span>)</span> <span>throws</span> <span>IOException</span> <span>{</span>
        <span>String</span> <span>resultJson</span> <span>=</span> <span>ActionResult</span><span>.</span><span>getFailedJson</span><span>(</span><span>errorMessage</span><span>);</span>
        <span>File</span> <span>tmpFile</span> <span>=</span> <span>File</span><span>.</span><span>createTempFile</span><span>(</span><span>"result"</span><span>,</span> <span>"json"</span><span>);</span>
        <span>try</span><span>(</span><span>FileOutputStream</span> <span>stream</span> <span>=</span> <span>new</span> <span>FileOutputStream</span><span>(</span><span>tmpFile</span><span>))</span> <span>{</span>
            <span>stream</span><span>.</span><span>write</span><span>(</span><span>resultJson</span><span>.</span><span>getBytes</span><span>());</span>
        <span>}</span>
        <span>return</span> <span>new</span> <span>SystemFile</span><span>(</span><span>tmpFile</span><span>).</span><span>attach</span><span>(</span><span>"result.json"</span><span>);</span>
    <span>}</span>
<span>}</span>
<span>package</span> <span>jp.masanori</span><span>;</span>

<span>import</span> <span>java.io.File</span><span>;</span>
<span>import</span> <span>java.io.FileOutputStream</span><span>;</span>
<span>import</span> <span>java.io.IOException</span><span>;</span>

<span>import</span> <span>com.fasterxml.jackson.core.JsonProcessingException</span><span>;</span>
<span>import</span> <span>com.fasterxml.jackson.databind.ObjectMapper</span><span>;</span>

<span>import</span> <span>io.micronaut.http.server.types.files.SystemFile</span><span>;</span>

<span>public</span> <span>class</span> <span>ActionResult</span> <span>{</span>
    <span>private</span> <span>boolean</span> <span>succeeded</span><span>;</span>
    <span>private</span> <span>String</span> <span>errorMessage</span><span>;</span>
    <span>public</span> <span>boolean</span> <span>isSucceeded</span><span>()</span> <span>{</span>
        <span>return</span> <span>succeeded</span><span>;</span>
    <span>}</span>
    <span>public</span> <span>String</span> <span>getErrorMessage</span><span>()</span> <span>{</span>
        <span>return</span> <span>errorMessage</span><span>;</span>
    <span>}</span>
    <span>public</span> <span>static</span> <span>ActionResult</span> <span>getSucceeded</span><span>()</span> <span>{</span>
        <span>ActionResult</span> <span>result</span> <span>=</span> <span>new</span> <span>ActionResult</span><span>();</span>
        <span>result</span><span>.</span><span>succeeded</span> <span>=</span> <span>true</span><span>;</span>
        <span>return</span> <span>result</span><span>;</span>
    <span>}</span>
    <span>public</span> <span>static</span> <span>ActionResult</span> <span>getFailed</span><span>(</span><span>String</span> <span>errorMessage</span><span>)</span> <span>{</span>
        <span>ActionResult</span> <span>result</span> <span>=</span> <span>new</span> <span>ActionResult</span><span>();</span>
        <span>result</span><span>.</span><span>errorMessage</span> <span>=</span> <span>errorMessage</span><span>;</span>
        <span>return</span> <span>result</span><span>;</span>
    <span>}</span>
    <span>public</span> <span>static</span> <span>String</span> <span>getFailedJson</span><span>(</span><span>String</span> <span>errorMessage</span><span>)</span> <span>throws</span> <span>JsonProcessingException</span> <span>{</span>
        <span>ActionResult</span> <span>result</span> <span>=</span> <span>ActionResult</span><span>.</span><span>getFailed</span><span>(</span><span>errorMessage</span><span>);</span>
        <span>ObjectMapper</span> <span>mapper</span> <span>=</span> <span>new</span> <span>ObjectMapper</span><span>();</span>
        <span>return</span> <span>mapper</span><span>.</span><span>writeValueAsString</span><span>(</span><span>result</span><span>);</span>
    <span>}</span>
    <span>public</span> <span>static</span> <span>SystemFile</span> <span>getFailedJsonFile</span><span>(</span><span>String</span> <span>errorMessage</span><span>)</span> <span>throws</span> <span>IOException</span> <span>{</span>
        <span>String</span> <span>resultJson</span> <span>=</span> <span>ActionResult</span><span>.</span><span>getFailedJson</span><span>(</span><span>errorMessage</span><span>);</span>
        <span>File</span> <span>tmpFile</span> <span>=</span> <span>File</span><span>.</span><span>createTempFile</span><span>(</span><span>"result"</span><span>,</span> <span>"json"</span><span>);</span>
        <span>try</span><span>(</span><span>FileOutputStream</span> <span>stream</span> <span>=</span> <span>new</span> <span>FileOutputStream</span><span>(</span><span>tmpFile</span><span>))</span> <span>{</span>
            <span>stream</span><span>.</span><span>write</span><span>(</span><span>resultJson</span><span>.</span><span>getBytes</span><span>());</span>
        <span>}</span>
        <span>return</span> <span>new</span> <span>SystemFile</span><span>(</span><span>tmpFile</span><span>).</span><span>attach</span><span>(</span><span>"result.json"</span><span>);</span>
    <span>}</span>
<span>}</span>
package jp.masanori;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

import io.micronaut.http.server.types.files.SystemFile;

public class ActionResult {
    private boolean succeeded;
    private String errorMessage;
    public boolean isSucceeded() {
        return succeeded;
    }
    public String getErrorMessage() {
        return errorMessage;
    }
    public static ActionResult getSucceeded() {
        ActionResult result = new ActionResult();
        result.succeeded = true;
        return result;
    }
    public static ActionResult getFailed(String errorMessage) {
        ActionResult result = new ActionResult();
        result.errorMessage = errorMessage;
        return result;
    }
    public static String getFailedJson(String errorMessage) throws JsonProcessingException {
        ActionResult result = ActionResult.getFailed(errorMessage);
        ObjectMapper mapper = new ObjectMapper();
        return mapper.writeValueAsString(result);
    }
    public static SystemFile getFailedJsonFile(String errorMessage) throws IOException {
        String resultJson = ActionResult.getFailedJson(errorMessage);
        File tmpFile = File.createTempFile("result", "json");
        try(FileOutputStream stream = new FileOutputStream(tmpFile)) {
            stream.write(resultJson.getBytes());
        }
        return new SystemFile(tmpFile).attach("result.json");
    }
}

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FileController.java 

<span>...</span>
    <span>@Get</span><span>(</span><span>uri</span><span>=</span><span>"zip"</span><span>)</span>
    <span>public</span> <span>HttpResponse</span><span><</span><span>SystemFile</span><span>></span> <span>getZip</span><span>()</span> <span>{</span>
        <span>SystemFile</span> <span>result</span> <span>=</span> <span>csvGen</span><span>.</span><span>generate</span><span>();</span>
        <span>if</span><span>(</span><span>result</span> <span>==</span> <span>null</span><span>)</span> <span>{</span>
            <span>try</span> <span>{</span>
                <span>return</span> <span>HttpResponse</span><span>.</span><span>ok</span><span>(</span><span>ActionResult</span><span>.</span><span>getFailedJsonFile</span><span>(</span><span>"Failed generating a Zip file"</span><span>));</span>
            <span>}</span> <span>catch</span><span>(</span><span>IOException</span> <span>ex</span><span>)</span> <span>{</span>
                <span>return</span> <span>HttpResponse</span><span>.</span><span>serverError</span><span>();</span>
            <span>}</span>
        <span>}</span>
        <span>return</span> <span>HttpResponse</span><span>.</span><span>ok</span><span>(</span><span>result</span><span>)</span>
            <span>.</span><span>contentType</span><span>(</span><span>"application/zip"</span><span>);</span>
    <span>}</span>
<span>...</span>
<span>...</span>
    <span>@Get</span><span>(</span><span>uri</span><span>=</span><span>"zip"</span><span>)</span>
    <span>public</span> <span>HttpResponse</span><span><</span><span>SystemFile</span><span>></span> <span>getZip</span><span>()</span> <span>{</span>
        <span>SystemFile</span> <span>result</span> <span>=</span> <span>csvGen</span><span>.</span><span>generate</span><span>();</span>
        <span>if</span><span>(</span><span>result</span> <span>==</span> <span>null</span><span>)</span> <span>{</span>
            <span>try</span> <span>{</span>
                <span>return</span> <span>HttpResponse</span><span>.</span><span>ok</span><span>(</span><span>ActionResult</span><span>.</span><span>getFailedJsonFile</span><span>(</span><span>"Failed generating a Zip file"</span><span>));</span>
            <span>}</span> <span>catch</span><span>(</span><span>IOException</span> <span>ex</span><span>)</span> <span>{</span>
                <span>return</span> <span>HttpResponse</span><span>.</span><span>serverError</span><span>();</span>
            <span>}</span>
        <span>}</span>
        <span>return</span> <span>HttpResponse</span><span>.</span><span>ok</span><span>(</span><span>result</span><span>)</span>
            <span>.</span><span>contentType</span><span>(</span><span>"application/zip"</span><span>);</span>
    <span>}</span>
<span>...</span>
...
    @Get(uri="zip")
    public HttpResponse<SystemFile> getZip() {
        SystemFile result = csvGen.generate();
        if(result == null) {
            try {
                return HttpResponse.ok(ActionResult.getFailedJsonFile("Failed generating a Zip file"));
            } catch(IOException ex) {
                return HttpResponse.serverError();
            }
        }
        return HttpResponse.ok(result)
            .contentType("application/zip");
    }
...

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原文链接：[Micronaut] Generating and downloading files as ZIP or JSON

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