CRUD Java, MySQL e JDBC

03811

Vou criar um guia CRUD (Create, Read, Update, Delete) em Java puro (usando JDBC para conexão com banco de dados). Usaremos o MySQL como exemplo, mas você pode adaptar para outros bancos.

Pré-requisitos

  1. Banco de dados MySQL instalado.
  2. Driver JDBC do MySQL (arquivo mysql-connector-java-X.X.XX.jar).
  3. Java 8 ou superior.

Passo 1: Configurar o Banco de Dados

Crie uma tabela usuarios no MySQL: 

<span>CREATE</span> <span>DATABASE</span> <span>crud_java</span><span>;</span>
<span>USE</span> <span>crud_java</span><span>;</span>
<span>CREATE</span> <span>TABLE</span> <span>usuarios</span> <span>(</span>
    <span>id</span> <span>INT</span> <span>PRIMARY</span> <span>KEY</span> <span>AUTO_INCREMENT</span><span>,</span>
    <span>nome</span> <span>VARCHAR</span><span>(</span><span>50</span><span>)</span> <span>NOT</span> <span>NULL</span><span>,</span>
    <span>email</span> <span>VARCHAR</span><span>(</span><span>50</span><span>)</span> <span>NOT</span> <span>NULL</span> <span>UNIQUE</span><span>,</span>
    <span>idade</span> <span>INT</span>
<span>);</span>
<span>CREATE</span> <span>DATABASE</span> <span>crud_java</span><span>;</span>
<span>USE</span> <span>crud_java</span><span>;</span>

<span>CREATE</span> <span>TABLE</span> <span>usuarios</span> <span>(</span>
    <span>id</span> <span>INT</span> <span>PRIMARY</span> <span>KEY</span> <span>AUTO_INCREMENT</span><span>,</span>
    <span>nome</span> <span>VARCHAR</span><span>(</span><span>50</span><span>)</span> <span>NOT</span> <span>NULL</span><span>,</span>
    <span>email</span> <span>VARCHAR</span><span>(</span><span>50</span><span>)</span> <span>NOT</span> <span>NULL</span> <span>UNIQUE</span><span>,</span>
    <span>idade</span> <span>INT</span>
<span>);</span>
CREATE DATABASE crud_java;
USE crud_java;

CREATE TABLE usuarios (
    id INT PRIMARY KEY AUTO_INCREMENT,
    nome VARCHAR(50) NOT NULL,
    email VARCHAR(50) NOT NULL UNIQUE,
    idade INT
);

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Passo 2: Estrutura do Projeto Java

Crie um projeto Java e adicione o driver JDBC ao classpath (dependência). 

src
└── main
    └── java
        ├── ConnectionFactory.java
        ├── UsuarioDAO.java
        └── Main.java
src
└── main
    └── java
        ├── ConnectionFactory.java
        ├── UsuarioDAO.java
        └── Main.java
src
└── main
    └── java
        ├── ConnectionFactory.java
        ├── UsuarioDAO.java
        └── Main.java

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Passo 3: Código Java

Classe ConnectionFactory (Conexão com o Banco) 

<span>import</span> <span>java.sql.Connection</span><span>;</span>
<span>import</span> <span>java.sql.DriverManager</span><span>;</span>
<span>import</span> <span>java.sql.SQLException</span><span>;</span>
<span>public</span> <span>class</span> <span>ConnectionFactory</span> <span>{</span>
    <span>private</span> <span>static</span> <span>final</span> <span>String</span> <span>URL</span> <span>=</span> <span>"jdbc:mysql://localhost:3306/crud_java"</span><span>;</span>
    <span>private</span> <span>static</span> <span>final</span> <span>String</span> <span>USER</span> <span>=</span> <span>"root"</span><span>;</span>
    <span>private</span> <span>static</span> <span>final</span> <span>String</span> <span>PASSWORD</span> <span>=</span> <span>"sua_senha"</span><span>;</span>
    <span>public</span> <span>static</span> <span>Connection</span> <span>getConnection</span><span>()</span> <span>{</span>
        <span>try</span> <span>{</span>
            <span>return</span> <span>DriverManager</span><span>.</span><span>getConnection</span><span>(</span><span>URL</span><span>,</span> <span>USER</span><span>,</span> <span>PASSWORD</span><span>);</span>
        <span>}</span> <span>catch</span> <span>(</span><span>SQLException</span> <span>e</span><span>)</span> <span>{</span>
            <span>throw</span> <span>new</span> <span>RuntimeException</span><span>(</span><span>"Erro ao conectar ao banco de dados"</span><span>,</span> <span>e</span><span>);</span>
        <span>}</span>
    <span>}</span>
<span>}</span>
<span>import</span> <span>java.sql.Connection</span><span>;</span>
<span>import</span> <span>java.sql.DriverManager</span><span>;</span>
<span>import</span> <span>java.sql.SQLException</span><span>;</span>

<span>public</span> <span>class</span> <span>ConnectionFactory</span> <span>{</span>
    <span>private</span> <span>static</span> <span>final</span> <span>String</span> <span>URL</span> <span>=</span> <span>"jdbc:mysql://localhost:3306/crud_java"</span><span>;</span>
    <span>private</span> <span>static</span> <span>final</span> <span>String</span> <span>USER</span> <span>=</span> <span>"root"</span><span>;</span>
    <span>private</span> <span>static</span> <span>final</span> <span>String</span> <span>PASSWORD</span> <span>=</span> <span>"sua_senha"</span><span>;</span>

    <span>public</span> <span>static</span> <span>Connection</span> <span>getConnection</span><span>()</span> <span>{</span>
        <span>try</span> <span>{</span>
            <span>return</span> <span>DriverManager</span><span>.</span><span>getConnection</span><span>(</span><span>URL</span><span>,</span> <span>USER</span><span>,</span> <span>PASSWORD</span><span>);</span>
        <span>}</span> <span>catch</span> <span>(</span><span>SQLException</span> <span>e</span><span>)</span> <span>{</span>
            <span>throw</span> <span>new</span> <span>RuntimeException</span><span>(</span><span>"Erro ao conectar ao banco de dados"</span><span>,</span> <span>e</span><span>);</span>
        <span>}</span>
    <span>}</span>
<span>}</span>
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class ConnectionFactory {
    private static final String URL = "jdbc:mysql://localhost:3306/crud_java";
    private static final String USER = "root";
    private static final String PASSWORD = "sua_senha";

    public static Connection getConnection() {
        try {
            return DriverManager.getConnection(URL, USER, PASSWORD);
        } catch (SQLException e) {
            throw new RuntimeException("Erro ao conectar ao banco de dados", e);
        }
    }
}

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Classe UsuarioDAO (Operações CRUD) 

<span>import</span> <span>java.sql.Connection</span><span>;</span>
<span>import</span> <span>java.sql.PreparedStatement</span><span>;</span>
<span>import</span> <span>java.sql.ResultSet</span><span>;</span>
<span>import</span> <span>java.sql.SQLException</span><span>;</span>
<span>import</span> <span>java.util.ArrayList</span><span>;</span>
<span>import</span> <span>java.util.List</span><span>;</span>
<span>public</span> <span>class</span> <span>UsuarioDAO</span> <span>{</span>
    <span>// CREATE</span>
    <span>public</span> <span>void</span> <span>create</span><span>(</span><span>Usuario</span> <span>usuario</span><span>)</span> <span>{</span>
        <span>String</span> <span>sql</span> <span>=</span> <span>"INSERT INTO usuarios (nome, email, idade) VALUES (?, ?, ?)"</span><span>;</span>
        <span>try</span> <span>(</span><span>Connection</span> <span>conn</span> <span>=</span> <span>ConnectionFactory</span><span>.</span><span>getConnection</span><span>();</span>
             <span>PreparedStatement</span> <span>stmt</span> <span>=</span> <span>conn</span><span>.</span><span>prepareStatement</span><span>(</span><span>sql</span><span>))</span> <span>{</span>
            <span>stmt</span><span>.</span><span>setString</span><span>(</span><span>1</span><span>,</span> <span>usuario</span><span>.</span><span>getNome</span><span>());</span>
            <span>stmt</span><span>.</span><span>setString</span><span>(</span><span>2</span><span>,</span> <span>usuario</span><span>.</span><span>getEmail</span><span>());</span>
            <span>stmt</span><span>.</span><span>setInt</span><span>(</span><span>3</span><span>,</span> <span>usuario</span><span>.</span><span>getIdade</span><span>());</span>
            <span>stmt</span><span>.</span><span>executeUpdate</span><span>();</span>
        <span>}</span> <span>catch</span> <span>(</span><span>SQLException</span> <span>e</span><span>)</span> <span>{</span>
            <span>throw</span> <span>new</span> <span>RuntimeException</span><span>(</span><span>"Erro ao criar usuário"</span><span>,</span> <span>e</span><span>);</span>
        <span>}</span>
    <span>}</span>
    <span>// READ</span>
    <span>public</span> <span>List</span><span><</span><span>Usuario</span><span>></span> <span>read</span><span>()</span> <span>{</span>
        <span>String</span> <span>sql</span> <span>=</span> <span>"SELECT * FROM usuarios"</span><span>;</span>
        <span>List</span><span><</span><span>Usuario</span><span>></span> <span>usuarios</span> <span>=</span> <span>new</span> <span>ArrayList</span><span><>();</span>
        <span>try</span> <span>(</span><span>Connection</span> <span>conn</span> <span>=</span> <span>ConnectionFactory</span><span>.</span><span>getConnection</span><span>();</span>
             <span>PreparedStatement</span> <span>stmt</span> <span>=</span> <span>conn</span><span>.</span><span>prepareStatement</span><span>(</span><span>sql</span><span>);</span>
             <span>ResultSet</span> <span>rs</span> <span>=</span> <span>stmt</span><span>.</span><span>executeQuery</span><span>())</span> <span>{</span>
            <span>while</span> <span>(</span><span>rs</span><span>.</span><span>next</span><span>())</span> <span>{</span>
                <span>Usuario</span> <span>usuario</span> <span>=</span> <span>new</span> <span>Usuario</span><span>(</span>
                    <span>rs</span><span>.</span><span>getInt</span><span>(</span><span>"id"</span><span>),</span>
                    <span>rs</span><span>.</span><span>getString</span><span>(</span><span>"nome"</span><span>),</span>
                    <span>rs</span><span>.</span><span>getString</span><span>(</span><span>"email"</span><span>),</span>
                    <span>rs</span><span>.</span><span>getInt</span><span>(</span><span>"idade"</span><span>)</span>
                <span>);</span>
                <span>usuarios</span><span>.</span><span>add</span><span>(</span><span>usuario</span><span>);</span>
            <span>}</span>
        <span>}</span> <span>catch</span> <span>(</span><span>SQLException</span> <span>e</span><span>)</span> <span>{</span>
            <span>throw</span> <span>new</span> <span>RuntimeException</span><span>(</span><span>"Erro ao listar usuários"</span><span>,</span> <span>e</span><span>);</span>
        <span>}</span>
        <span>return</span> <span>usuarios</span><span>;</span>
    <span>}</span>
    <span>// UPDATE</span>
    <span>public</span> <span>void</span> <span>update</span><span>(</span><span>Usuario</span> <span>usuario</span><span>)</span> <span>{</span>
        <span>String</span> <span>sql</span> <span>=</span> <span>"UPDATE usuarios SET nome = ?, email = ?, idade = ? WHERE id = ?"</span><span>;</span>
        <span>try</span> <span>(</span><span>Connection</span> <span>conn</span> <span>=</span> <span>ConnectionFactory</span><span>.</span><span>getConnection</span><span>();</span>
             <span>PreparedStatement</span> <span>stmt</span> <span>=</span> <span>conn</span><span>.</span><span>prepareStatement</span><span>(</span><span>sql</span><span>))</span> <span>{</span>
            <span>stmt</span><span>.</span><span>setString</span><span>(</span><span>1</span><span>,</span> <span>usuario</span><span>.</span><span>getNome</span><span>());</span>
            <span>stmt</span><span>.</span><span>setString</span><span>(</span><span>2</span><span>,</span> <span>usuario</span><span>.</span><span>getEmail</span><span>());</span>
            <span>stmt</span><span>.</span><span>setInt</span><span>(</span><span>3</span><span>,</span> <span>usuario</span><span>.</span><span>getIdade</span><span>());</span>
            <span>stmt</span><span>.</span><span>setInt</span><span>(</span><span>4</span><span>,</span> <span>usuario</span><span>.</span><span>getId</span><span>());</span>
            <span>stmt</span><span>.</span><span>executeUpdate</span><span>();</span>
        <span>}</span> <span>catch</span> <span>(</span><span>SQLException</span> <span>e</span><span>)</span> <span>{</span>
            <span>throw</span> <span>new</span> <span>RuntimeException</span><span>(</span><span>"Erro ao atualizar usuário"</span><span>,</span> <span>e</span><span>);</span>
        <span>}</span>
    <span>}</span>
    <span>// DELETE</span>
    <span>public</span> <span>void</span> <span>delete</span><span>(</span><span>int</span> <span>id</span><span>)</span> <span>{</span>
        <span>String</span> <span>sql</span> <span>=</span> <span>"DELETE FROM usuarios WHERE id = ?"</span><span>;</span>
        <span>try</span> <span>(</span><span>Connection</span> <span>conn</span> <span>=</span> <span>ConnectionFactory</span><span>.</span><span>getConnection</span><span>();</span>
             <span>PreparedStatement</span> <span>stmt</span> <span>=</span> <span>conn</span><span>.</span><span>prepareStatement</span><span>(</span><span>sql</span><span>))</span> <span>{</span>
            <span>stmt</span><span>.</span><span>setInt</span><span>(</span><span>1</span><span>,</span> <span>id</span><span>);</span>
            <span>stmt</span><span>.</span><span>executeUpdate</span><span>();</span>
        <span>}</span> <span>catch</span> <span>(</span><span>SQLException</span> <span>e</span><span>)</span> <span>{</span>
            <span>throw</span> <span>new</span> <span>RuntimeException</span><span>(</span><span>"Erro ao deletar usuário"</span><span>,</span> <span>e</span><span>);</span>
        <span>}</span>
    <span>}</span>
<span>}</span>
<span>import</span> <span>java.sql.Connection</span><span>;</span>
<span>import</span> <span>java.sql.PreparedStatement</span><span>;</span>
<span>import</span> <span>java.sql.ResultSet</span><span>;</span>
<span>import</span> <span>java.sql.SQLException</span><span>;</span>
<span>import</span> <span>java.util.ArrayList</span><span>;</span>
<span>import</span> <span>java.util.List</span><span>;</span>

<span>public</span> <span>class</span> <span>UsuarioDAO</span> <span>{</span>

    <span>// CREATE</span>
    <span>public</span> <span>void</span> <span>create</span><span>(</span><span>Usuario</span> <span>usuario</span><span>)</span> <span>{</span>
        <span>String</span> <span>sql</span> <span>=</span> <span>"INSERT INTO usuarios (nome, email, idade) VALUES (?, ?, ?)"</span><span>;</span>
        <span>try</span> <span>(</span><span>Connection</span> <span>conn</span> <span>=</span> <span>ConnectionFactory</span><span>.</span><span>getConnection</span><span>();</span>
             <span>PreparedStatement</span> <span>stmt</span> <span>=</span> <span>conn</span><span>.</span><span>prepareStatement</span><span>(</span><span>sql</span><span>))</span> <span>{</span>

            <span>stmt</span><span>.</span><span>setString</span><span>(</span><span>1</span><span>,</span> <span>usuario</span><span>.</span><span>getNome</span><span>());</span>
            <span>stmt</span><span>.</span><span>setString</span><span>(</span><span>2</span><span>,</span> <span>usuario</span><span>.</span><span>getEmail</span><span>());</span>
            <span>stmt</span><span>.</span><span>setInt</span><span>(</span><span>3</span><span>,</span> <span>usuario</span><span>.</span><span>getIdade</span><span>());</span>
            <span>stmt</span><span>.</span><span>executeUpdate</span><span>();</span>

        <span>}</span> <span>catch</span> <span>(</span><span>SQLException</span> <span>e</span><span>)</span> <span>{</span>
            <span>throw</span> <span>new</span> <span>RuntimeException</span><span>(</span><span>"Erro ao criar usuário"</span><span>,</span> <span>e</span><span>);</span>
        <span>}</span>
    <span>}</span>

    <span>// READ</span>
    <span>public</span> <span>List</span><span><</span><span>Usuario</span><span>></span> <span>read</span><span>()</span> <span>{</span>
        <span>String</span> <span>sql</span> <span>=</span> <span>"SELECT * FROM usuarios"</span><span>;</span>
        <span>List</span><span><</span><span>Usuario</span><span>></span> <span>usuarios</span> <span>=</span> <span>new</span> <span>ArrayList</span><span><>();</span>

        <span>try</span> <span>(</span><span>Connection</span> <span>conn</span> <span>=</span> <span>ConnectionFactory</span><span>.</span><span>getConnection</span><span>();</span>
             <span>PreparedStatement</span> <span>stmt</span> <span>=</span> <span>conn</span><span>.</span><span>prepareStatement</span><span>(</span><span>sql</span><span>);</span>
             <span>ResultSet</span> <span>rs</span> <span>=</span> <span>stmt</span><span>.</span><span>executeQuery</span><span>())</span> <span>{</span>

            <span>while</span> <span>(</span><span>rs</span><span>.</span><span>next</span><span>())</span> <span>{</span>
                <span>Usuario</span> <span>usuario</span> <span>=</span> <span>new</span> <span>Usuario</span><span>(</span>
                    <span>rs</span><span>.</span><span>getInt</span><span>(</span><span>"id"</span><span>),</span>
                    <span>rs</span><span>.</span><span>getString</span><span>(</span><span>"nome"</span><span>),</span>
                    <span>rs</span><span>.</span><span>getString</span><span>(</span><span>"email"</span><span>),</span>
                    <span>rs</span><span>.</span><span>getInt</span><span>(</span><span>"idade"</span><span>)</span>
                <span>);</span>
                <span>usuarios</span><span>.</span><span>add</span><span>(</span><span>usuario</span><span>);</span>
            <span>}</span>

        <span>}</span> <span>catch</span> <span>(</span><span>SQLException</span> <span>e</span><span>)</span> <span>{</span>
            <span>throw</span> <span>new</span> <span>RuntimeException</span><span>(</span><span>"Erro ao listar usuários"</span><span>,</span> <span>e</span><span>);</span>
        <span>}</span>
        <span>return</span> <span>usuarios</span><span>;</span>
    <span>}</span>

    <span>// UPDATE</span>
    <span>public</span> <span>void</span> <span>update</span><span>(</span><span>Usuario</span> <span>usuario</span><span>)</span> <span>{</span>
        <span>String</span> <span>sql</span> <span>=</span> <span>"UPDATE usuarios SET nome = ?, email = ?, idade = ? WHERE id = ?"</span><span>;</span>
        <span>try</span> <span>(</span><span>Connection</span> <span>conn</span> <span>=</span> <span>ConnectionFactory</span><span>.</span><span>getConnection</span><span>();</span>
             <span>PreparedStatement</span> <span>stmt</span> <span>=</span> <span>conn</span><span>.</span><span>prepareStatement</span><span>(</span><span>sql</span><span>))</span> <span>{</span>

            <span>stmt</span><span>.</span><span>setString</span><span>(</span><span>1</span><span>,</span> <span>usuario</span><span>.</span><span>getNome</span><span>());</span>
            <span>stmt</span><span>.</span><span>setString</span><span>(</span><span>2</span><span>,</span> <span>usuario</span><span>.</span><span>getEmail</span><span>());</span>
            <span>stmt</span><span>.</span><span>setInt</span><span>(</span><span>3</span><span>,</span> <span>usuario</span><span>.</span><span>getIdade</span><span>());</span>
            <span>stmt</span><span>.</span><span>setInt</span><span>(</span><span>4</span><span>,</span> <span>usuario</span><span>.</span><span>getId</span><span>());</span>
            <span>stmt</span><span>.</span><span>executeUpdate</span><span>();</span>

        <span>}</span> <span>catch</span> <span>(</span><span>SQLException</span> <span>e</span><span>)</span> <span>{</span>
            <span>throw</span> <span>new</span> <span>RuntimeException</span><span>(</span><span>"Erro ao atualizar usuário"</span><span>,</span> <span>e</span><span>);</span>
        <span>}</span>
    <span>}</span>

    <span>// DELETE</span>
    <span>public</span> <span>void</span> <span>delete</span><span>(</span><span>int</span> <span>id</span><span>)</span> <span>{</span>
        <span>String</span> <span>sql</span> <span>=</span> <span>"DELETE FROM usuarios WHERE id = ?"</span><span>;</span>
        <span>try</span> <span>(</span><span>Connection</span> <span>conn</span> <span>=</span> <span>ConnectionFactory</span><span>.</span><span>getConnection</span><span>();</span>
             <span>PreparedStatement</span> <span>stmt</span> <span>=</span> <span>conn</span><span>.</span><span>prepareStatement</span><span>(</span><span>sql</span><span>))</span> <span>{</span>

            <span>stmt</span><span>.</span><span>setInt</span><span>(</span><span>1</span><span>,</span> <span>id</span><span>);</span>
            <span>stmt</span><span>.</span><span>executeUpdate</span><span>();</span>

        <span>}</span> <span>catch</span> <span>(</span><span>SQLException</span> <span>e</span><span>)</span> <span>{</span>
            <span>throw</span> <span>new</span> <span>RuntimeException</span><span>(</span><span>"Erro ao deletar usuário"</span><span>,</span> <span>e</span><span>);</span>
        <span>}</span>
    <span>}</span>
<span>}</span>
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class UsuarioDAO {

    // CREATE
    public void create(Usuario usuario) {
        String sql = "INSERT INTO usuarios (nome, email, idade) VALUES (?, ?, ?)";
        try (Connection conn = ConnectionFactory.getConnection();
             PreparedStatement stmt = conn.prepareStatement(sql)) {

            stmt.setString(1, usuario.getNome());
            stmt.setString(2, usuario.getEmail());
            stmt.setInt(3, usuario.getIdade());
            stmt.executeUpdate();

        } catch (SQLException e) {
            throw new RuntimeException("Erro ao criar usuário", e);
        }
    }

    // READ
    public List<Usuario> read() {
        String sql = "SELECT * FROM usuarios";
        List<Usuario> usuarios = new ArrayList<>();

        try (Connection conn = ConnectionFactory.getConnection();
             PreparedStatement stmt = conn.prepareStatement(sql);
             ResultSet rs = stmt.executeQuery()) {

            while (rs.next()) {
                Usuario usuario = new Usuario(
                    rs.getInt("id"),
                    rs.getString("nome"),
                    rs.getString("email"),
                    rs.getInt("idade")
                );
                usuarios.add(usuario);
            }

        } catch (SQLException e) {
            throw new RuntimeException("Erro ao listar usuários", e);
        }
        return usuarios;
    }

    // UPDATE
    public void update(Usuario usuario) {
        String sql = "UPDATE usuarios SET nome = ?, email = ?, idade = ? WHERE id = ?";
        try (Connection conn = ConnectionFactory.getConnection();
             PreparedStatement stmt = conn.prepareStatement(sql)) {

            stmt.setString(1, usuario.getNome());
            stmt.setString(2, usuario.getEmail());
            stmt.setInt(3, usuario.getIdade());
            stmt.setInt(4, usuario.getId());
            stmt.executeUpdate();

        } catch (SQLException e) {
            throw new RuntimeException("Erro ao atualizar usuário", e);
        }
    }

    // DELETE
    public void delete(int id) {
        String sql = "DELETE FROM usuarios WHERE id = ?";
        try (Connection conn = ConnectionFactory.getConnection();
             PreparedStatement stmt = conn.prepareStatement(sql)) {

            stmt.setInt(1, id);
            stmt.executeUpdate();

        } catch (SQLException e) {
            throw new RuntimeException("Erro ao deletar usuário", e);
        }
    }
}

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Classe Usuario (Modelo) 

<span>public</span> <span>class</span> <span>Usuario</span> <span>{</span>
    <span>private</span> <span>int</span> <span>id</span><span>;</span>
    <span>private</span> <span>String</span> <span>nome</span><span>;</span>
    <span>private</span> <span>String</span> <span>email</span><span>;</span>
    <span>private</span> <span>int</span> <span>idade</span><span>;</span>
    <span>// Construtor, getters e setters</span>
    <span>public</span> <span>Usuario</span><span>(</span><span>int</span> <span>id</span><span>,</span> <span>String</span> <span>nome</span><span>,</span> <span>String</span> <span>email</span><span>,</span> <span>int</span> <span>idade</span><span>)</span> <span>{</span>
        <span>this</span><span>.</span><span>id</span> <span>=</span> <span>id</span><span>;</span>
        <span>this</span><span>.</span><span>nome</span> <span>=</span> <span>nome</span><span>;</span>
        <span>this</span><span>.</span><span>email</span> <span>=</span> <span>email</span><span>;</span>
        <span>this</span><span>.</span><span>idade</span> <span>=</span> <span>idade</span><span>;</span>
    <span>}</span>
    <span>// Getters e Setters</span>
    <span>public</span> <span>int</span> <span>getId</span><span>()</span> <span>{</span> <span>return</span> <span>id</span><span>;</span> <span>}</span>
    <span>public</span> <span>String</span> <span>getNome</span><span>()</span> <span>{</span> <span>return</span> <span>nome</span><span>;</span> <span>}</span>
    <span>public</span> <span>String</span> <span>getEmail</span><span>()</span> <span>{</span> <span>return</span> <span>email</span><span>;</span> <span>}</span>
    <span>public</span> <span>int</span> <span>getIdade</span><span>()</span> <span>{</span> <span>return</span> <span>idade</span><span>;</span> <span>}</span>
<span>}</span>
<span>public</span> <span>class</span> <span>Usuario</span> <span>{</span>
    <span>private</span> <span>int</span> <span>id</span><span>;</span>
    <span>private</span> <span>String</span> <span>nome</span><span>;</span>
    <span>private</span> <span>String</span> <span>email</span><span>;</span>
    <span>private</span> <span>int</span> <span>idade</span><span>;</span>

    <span>// Construtor, getters e setters</span>
    <span>public</span> <span>Usuario</span><span>(</span><span>int</span> <span>id</span><span>,</span> <span>String</span> <span>nome</span><span>,</span> <span>String</span> <span>email</span><span>,</span> <span>int</span> <span>idade</span><span>)</span> <span>{</span>
        <span>this</span><span>.</span><span>id</span> <span>=</span> <span>id</span><span>;</span>
        <span>this</span><span>.</span><span>nome</span> <span>=</span> <span>nome</span><span>;</span>
        <span>this</span><span>.</span><span>email</span> <span>=</span> <span>email</span><span>;</span>
        <span>this</span><span>.</span><span>idade</span> <span>=</span> <span>idade</span><span>;</span>
    <span>}</span>

    <span>// Getters e Setters</span>
    <span>public</span> <span>int</span> <span>getId</span><span>()</span> <span>{</span> <span>return</span> <span>id</span><span>;</span> <span>}</span>
    <span>public</span> <span>String</span> <span>getNome</span><span>()</span> <span>{</span> <span>return</span> <span>nome</span><span>;</span> <span>}</span>
    <span>public</span> <span>String</span> <span>getEmail</span><span>()</span> <span>{</span> <span>return</span> <span>email</span><span>;</span> <span>}</span>
    <span>public</span> <span>int</span> <span>getIdade</span><span>()</span> <span>{</span> <span>return</span> <span>idade</span><span>;</span> <span>}</span>
<span>}</span>
public class Usuario {
    private int id;
    private String nome;
    private String email;
    private int idade;

    // Construtor, getters e setters
    public Usuario(int id, String nome, String email, int idade) {
        this.id = id;
        this.nome = nome;
        this.email = email;
        this.idade = idade;
    }

    // Getters e Setters
    public int getId() { return id; }
    public String getNome() { return nome; }
    public String getEmail() { return email; }
    public int getIdade() { return idade; }
}

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Classe Main (Teste) 

<span>import</span> <span>java.util.List</span><span>;</span>
<span>public</span> <span>class</span> <span>Main</span> <span>{</span>
    <span>public</span> <span>static</span> <span>void</span> <span>main</span><span>(</span><span>String</span><span>[]</span> <span>args</span><span>)</span> <span>{</span>
        <span>UsuarioDAO</span> <span>usuarioDAO</span> <span>=</span> <span>new</span> <span>UsuarioDAO</span><span>();</span>
        <span>// CREATE</span>
        <span>Usuario</span> <span>novoUsuario</span> <span>=</span> <span>new</span> <span>Usuario</span><span>(</span><span>0</span><span>,</span> <span>"João Silva"</span><span>,</span> <span>"joao@email.com"</span><span>,</span> <span>30</span><span>);</span>
        <span>usuarioDAO</span><span>.</span><span>create</span><span>(</span><span>novoUsuario</span><span>);</span>
        <span>// READ</span>
        <span>List</span><span><</span><span>Usuario</span><span>></span> <span>usuarios</span> <span>=</span> <span>usuarioDAO</span><span>.</span><span>read</span><span>();</span>
        <span>for</span> <span>(</span><span>Usuario</span> <span>u</span> <span>:</span> <span>usuarios</span><span>)</span> <span>{</span>
            <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>u</span><span>.</span><span>getId</span><span>()</span> <span>+</span> <span>" - "</span> <span>+</span> <span>u</span><span>.</span><span>getNome</span><span>());</span>
        <span>}</span>
        <span>// UPDATE</span>
        <span>Usuario</span> <span>usuarioAtualizado</span> <span>=</span> <span>new</span> <span>Usuario</span><span>(</span><span>1</span><span>,</span> <span>"João Silva Atualizado"</span><span>,</span> <span>"joao.novo@email.com"</span><span>,</span> <span>35</span><span>);</span>
        <span>usuarioDAO</span><span>.</span><span>update</span><span>(</span><span>usuarioAtualizado</span><span>);</span>
        <span>// DELETE</span>
        <span>usuarioDAO</span><span>.</span><span>delete</span><span>(</span><span>1</span><span>);</span>
    <span>}</span>
<span>}</span>
<span>import</span> <span>java.util.List</span><span>;</span>

<span>public</span> <span>class</span> <span>Main</span> <span>{</span>
    <span>public</span> <span>static</span> <span>void</span> <span>main</span><span>(</span><span>String</span><span>[]</span> <span>args</span><span>)</span> <span>{</span>
        <span>UsuarioDAO</span> <span>usuarioDAO</span> <span>=</span> <span>new</span> <span>UsuarioDAO</span><span>();</span>

        <span>// CREATE</span>
        <span>Usuario</span> <span>novoUsuario</span> <span>=</span> <span>new</span> <span>Usuario</span><span>(</span><span>0</span><span>,</span> <span>"João Silva"</span><span>,</span> <span>"joao@email.com"</span><span>,</span> <span>30</span><span>);</span>
        <span>usuarioDAO</span><span>.</span><span>create</span><span>(</span><span>novoUsuario</span><span>);</span>

        <span>// READ</span>
        <span>List</span><span><</span><span>Usuario</span><span>></span> <span>usuarios</span> <span>=</span> <span>usuarioDAO</span><span>.</span><span>read</span><span>();</span>
        <span>for</span> <span>(</span><span>Usuario</span> <span>u</span> <span>:</span> <span>usuarios</span><span>)</span> <span>{</span>
            <span>System</span><span>.</span><span>out</span><span>.</span><span>println</span><span>(</span><span>u</span><span>.</span><span>getId</span><span>()</span> <span>+</span> <span>" - "</span> <span>+</span> <span>u</span><span>.</span><span>getNome</span><span>());</span>
        <span>}</span>

        <span>// UPDATE</span>
        <span>Usuario</span> <span>usuarioAtualizado</span> <span>=</span> <span>new</span> <span>Usuario</span><span>(</span><span>1</span><span>,</span> <span>"João Silva Atualizado"</span><span>,</span> <span>"joao.novo@email.com"</span><span>,</span> <span>35</span><span>);</span>
        <span>usuarioDAO</span><span>.</span><span>update</span><span>(</span><span>usuarioAtualizado</span><span>);</span>

        <span>// DELETE</span>
        <span>usuarioDAO</span><span>.</span><span>delete</span><span>(</span><span>1</span><span>);</span>
    <span>}</span>
<span>}</span>
import java.util.List;

public class Main {
    public static void main(String[] args) {
        UsuarioDAO usuarioDAO = new UsuarioDAO();

        // CREATE
        Usuario novoUsuario = new Usuario(0, "João Silva", "joao@email.com", 30);
        usuarioDAO.create(novoUsuario);

        // READ
        List<Usuario> usuarios = usuarioDAO.read();
        for (Usuario u : usuarios) {
            System.out.println(u.getId() + " - " + u.getNome());
        }

        // UPDATE
        Usuario usuarioAtualizado = new Usuario(1, "João Silva Atualizado", "joao.novo@email.com", 35);
        usuarioDAO.update(usuarioAtualizado);

        // DELETE
        usuarioDAO.delete(1);
    }
}

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Passo 4: Execução

  1. Adicione o driver JDBC ao classpath (no Eclipse: Botão direito no projeto > Build Path > Configure Build Path > Libraries > Add JARs).
  2. Execute a classe Main.

Considerações

  1. Tratamento de Exceções: Use try-with-resources para garantir que conexões sejam fechadas automaticamente.
  2. Segurança: Use PreparedStatement para evitar SQL injection.
  3. Transações: Para operações críticas, adicione controle transacional com commit() e rollback().

Este é um exemplo básico. Para projetos reais, considere usar:

  • Frameworks como Hibernate (JPA) ou Spring JDBC.
  • Pool de conexões (ex: HikariCP).
  • Tratamento mais robusto de exceções.

原文链接：CRUD Java, MySQL e JDBC

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