Quando usar ResponseEntity?

Vejamos a controller com o endpoint abaixo:

<span>@RestController</span>
<span>@RequestMapping</span><span>(</span><span>"v1/hello"</span><span>)</span>
<span>public</span> <span>class</span> <span>ExampleController</span> <span>{</span>
    <span>@GetMapping</span>
    <span>public</span> <span>ResponseEntity</span><span><</span><span>String</span><span>></span> <span>get</span><span>()</span> <span>{</span>
        <span>return</span> <span>ResponseEntity</span><span>.</span><span>ok</span><span>(</span><span>"Hello World!"</span><span>);</span>
    <span>}</span>
<span>}</span>
<span>@RestController</span>
<span>@RequestMapping</span><span>(</span><span>"v1/hello"</span><span>)</span>
<span>public</span> <span>class</span> <span>ExampleController</span> <span>{</span>

    <span>@GetMapping</span>
    <span>public</span> <span>ResponseEntity</span><span><</span><span>String</span><span>></span> <span>get</span><span>()</span> <span>{</span>
        <span>return</span> <span>ResponseEntity</span><span>.</span><span>ok</span><span>(</span><span>"Hello World!"</span><span>);</span>
    <span>}</span>
<span>}</span>
@RestController
@RequestMapping("v1/hello")
public class ExampleController {

    @GetMapping
    public ResponseEntity<String> get() {
        return ResponseEntity.ok("Hello World!");
    }
}

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Quando se utiliza a anotação @RestController do Spring, por default os responses são colocados nos body’s das respostas, é desnecessário o uso de ResponseEntity tipificando o retorno do método, apenas o tipo da resposta diretamente, como no exemplo abaixo:

<span>@RestController</span>
<span>@RequestMapping</span><span>(</span><span>"v1/hello"</span><span>)</span>
<span>public</span> <span>class</span> <span>ExampleController</span> <span>{</span>
    <span>@GetMapping</span>
    <span>public</span> <span>String</span> <span>get</span><span>()</span> <span>{</span>
        <span>return</span> <span>"Hello World!"</span><span>;</span>
    <span>}</span>
<span>}</span>
<span>@RestController</span>
<span>@RequestMapping</span><span>(</span><span>"v1/hello"</span><span>)</span>
<span>public</span> <span>class</span> <span>ExampleController</span> <span>{</span>

    <span>@GetMapping</span>
    <span>public</span> <span>String</span> <span>get</span><span>()</span> <span>{</span>
        <span>return</span> <span>"Hello World!"</span><span>;</span>
    <span>}</span>
<span>}</span>
@RestController
@RequestMapping("v1/hello")
public class ExampleController {

    @GetMapping
    public String get() {
        return "Hello World!";
    }
}

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Também, por default, no caso de sucesso, o status code utilizado nos enpoints é 200 (OK), ou seja, só se faz necessário alterá-lo quando é desejado utilizar outro status, e não precisa ser utilizado ResponseEntity, basta utilizar a anotação @ResponseStatus acima do método:

<span>@RestController</span>
<span>@RequestMapping</span><span>(</span><span>"v1/hello"</span><span>)</span>
<span>public</span> <span>class</span> <span>ExampleController</span> <span>{</span>
    <span>@GetMapping</span>
    <span>@ResponseStatus</span><span>(</span><span>HttpStatus</span><span>.</span><span>ACCEPTED</span><span>)</span>
    <span>public</span> <span>String</span> <span>get</span><span>()</span> <span>{</span>
        <span>return</span> <span>"Hello World!"</span><span>;</span>
    <span>}</span>
<span>}</span>
<span>@RestController</span>
<span>@RequestMapping</span><span>(</span><span>"v1/hello"</span><span>)</span>
<span>public</span> <span>class</span> <span>ExampleController</span> <span>{</span>

    <span>@GetMapping</span>
    <span>@ResponseStatus</span><span>(</span><span>HttpStatus</span><span>.</span><span>ACCEPTED</span><span>)</span>
    <span>public</span> <span>String</span> <span>get</span><span>()</span> <span>{</span>
        <span>return</span> <span>"Hello World!"</span><span>;</span>
    <span>}</span>
<span>}</span>
@RestController
@RequestMapping("v1/hello")
public class ExampleController {

    @GetMapping
    @ResponseStatus(HttpStatus.ACCEPTED)
    public String get() {
        return "Hello World!";
    }
}

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Então porque existe a ResponseEntity?

Para casos em que você precisa adicionar mais informações na resposta que não apenas o body e o status, como por exemplo adicionar um header ao response:

<span>@RestController</span>
<span>@RequestMapping</span><span>(</span><span>"v1/hello"</span><span>)</span>
<span>public</span> <span>class</span> <span>ExampleController</span> <span>{</span>
    <span>@GetMapping</span>
    <span>public</span> <span>ResponseEntity</span><span><</span><span>String</span><span>></span> <span>get</span><span>()</span> <span>{</span>
        <span>return</span> <span>ResponseEntity</span><span>.</span><span>ok</span><span>()</span>
            <span>.</span><span>header</span><span>(</span><span>"X-Test"</span><span>,</span> <span>"Blabla"</span><span>)</span>
            <span>.</span><span>body</span><span>(</span><span>"Hello World!"</span><span>);</span>
    <span>}</span>
<span>}</span>
<span>@RestController</span>
<span>@RequestMapping</span><span>(</span><span>"v1/hello"</span><span>)</span>
<span>public</span> <span>class</span> <span>ExampleController</span> <span>{</span>

    <span>@GetMapping</span>
    <span>public</span> <span>ResponseEntity</span><span><</span><span>String</span><span>></span> <span>get</span><span>()</span> <span>{</span>
        <span>return</span> <span>ResponseEntity</span><span>.</span><span>ok</span><span>()</span>
            <span>.</span><span>header</span><span>(</span><span>"X-Test"</span><span>,</span> <span>"Blabla"</span><span>)</span>
            <span>.</span><span>body</span><span>(</span><span>"Hello World!"</span><span>);</span>
    <span>}</span>
<span>}</span>
@RestController
@RequestMapping("v1/hello")
public class ExampleController {

    @GetMapping
    public ResponseEntity<String> get() {
        return ResponseEntity.ok()
            .header("X-Test", "Blabla")
            .body("Hello World!");
    }
}

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原文链接：Quando usar ResponseEntity?