SpringMVC-Handler-Return Values返回值

Handler-Return Values返回值

支持的返回类型列表

The table below shows supported controller method return values. Reactive types are supported for all return values, see below for more details.

Controller method return value	Description
@ResponseBody	The return value is converted through HttpMessageConverters and written to the response. See @ResponseBody. 返回值通过HttpMessageConverters转换并写入响应。请参阅@ResponseBody。处理器功能处理方法的返回值作为响应体（通过HttpMessageConverter进行类型转换）；作用：该注解用于将Controller的方法返回的对象，通过适当的HttpMessageConverter转换为指定格式后，写入到Response对象的body数据区。使用时机：返回的数据不是html标签的页面，而是其他某种格式的数据时（如json、xml等）使用；
HttpEntity<B>, ResponseEntity<B>	The return value specifies the full response including HTTP headers and body be converted through HttpMessageConverters and written to the response. See ResponseEntity. 返回值指定完整响应，包括HTTP标头和正文通过HttpMessageConverters转换并写入响应。请参阅ResponseEntity。
HttpHeaders	For returning a response with headers and no body. 为了返回一个响应头和没有正文。
String	A view name to be resolved with ViewResolver's and used together with the implicit model — determined through command objects and @ModelAttribute methods. The handler method may also programmatically enrich the model by declaring a Model argument (see above). 一个视图名称，用ViewResolver解决，并与隐式模型一起使用 - 通过命令对象和@ModelAttribute方法确定。处理程序方法也可以通过声明一个Model参数来以编程方式丰富模型（参见上文）。
View	A View instance to use for rendering together with the implicit model — determined through command objects and @ModelAttribute methods. The handler method may also programmatically enrich the model by declaring a Model argument (see above). 用于与隐式模型一起渲染的View实例 - 通过命令对象和@ModelAttribute方法确定。处理程序方法也可以通过声明一个Model参数来以编程方式丰富模型（参见上文）。
java.util.Map, org.springframework.ui.Model	Attributes to be added to the implicit model with the view name implicitly determined through a RequestToViewNameTranslator. 要通过RequestToViewNameTranslator隐式确定的视图名称添加到隐式模型的属性。
@ModelAttribute	An attribute to be added to the model with the view name implicitly determined through a RequestToViewNameTranslator. Note that @ModelAttribute is optional. See "Any other return value" further below in this table. 要通过RequestToViewNameTranslator隐式确定的视图名称添加到模型的属性。请注意@ModelAttribute是可选的。请参阅本表下面的“任何其他返回值”。
ModelAndView object	The view and model attributes to use, and optionally a response status. 要使用的视图和模型属性，以及可选的响应状态。
void	A method with a void return type (or null return value) is considered to have fully handled the response if it also has a ServletResponse, or an OutputStream argument, or an @ResponseStatus annotation. The same is true also if the controller has made a positive ETag or lastModified timestamp check (see @Controller caching for details). If none of the above is true, a void return type may also indicate "no response body" for REST controllers, or default view name selection for HTML controllers. 具有void返回类型（或返回值为null）的方法如果还有ServletResponse，OutputStream参数或@ResponseStatus注释，则认为它已完全处理响应。如果控制器进行了积极的ETag或lastModified时间戳检查（请参阅@Controller缓存了解详细信息），情况也是如此。如果以上都不是这样，那么void返回类型也可能指示REST控制器的“无响应主体”，或HTML控制器的默认视图名称选择。
DeferredResult<V>	Produce any of the above return values asynchronously from any thread — e.g. possibly as a result of some event or callback. See Async Requests and DeferredResult. 从任何线程异步生成任何上述返回值 - 例如可能是由于某些事件或回调。请参阅异步请求和延期结果。
Callable<V>	Produce any of the above return values asynchronously in a Spring MVC managed thread. See Async Requests and Callable.
ListenableFuture<V>, java.util.concurrent.CompletionStage<V>, java.util.concurrent.CompletableFuture<V>	Alternative to DeferredResult as a convenience for example when an underlying service returns one of those. 在Spring MVC托管线程中异步生成上述任何返回值。请参阅异步请求和可调用
ResponseBodyEmitter, SseEmitter	Emit a stream of objects asynchronously to be written to the response with HttpMessageConverter's; also supported as the body of a ResponseEntity. See Async Requests and HTTP Streaming. 用HttpMessageConverter's异步发出一个对象流写入响应; 也支持作为ResponseEntity的主体。请参阅异步请求和HTTP流。
StreamingResponseBody	Write to the response OutputStream asynchronously; also supported as the body of a ResponseEntity. See Async Requests and HTTP Streaming. 异步写入响应的OutputStream; 也支持作为ResponseEntity的主体。请参阅异步请求和HTTP流程。
Reactive types — Reactor, RxJava, or others via ReactiveAdapterRegistry	Alternative to `DeferredResult with multi-value streams (e.g. Flux, Observable) collected to a List. For streaming scenarios — e.g. text/event-stream, application/json+stream — SseEmitter and ResponseBodyEmitter are used instead, where ServletOutputStream blocking I/O is performed on a Spring MVC managed thread and back pressure applied against the completion of each write. See Async Requests and Reactive types. 具有多值流的DeferredResult（例如Flux，Observable）的替代方法被收集到列表中。对于流式场景 - 例如 text / event-stream，application / json + stream - 使用SseEmitter和ResponseBodyEmitter，而在Spring MVC托管线程上执行ServletOutputStream阻塞I / O，并在每次写入完成时施加背压。请参阅异步请求和反应类型。
Any other return value	If a return value is not matched to any of the above, by default it is treated as a view name, if it is String or void (default view name selection via RequestToViewNameTranslator applies); or as a model attribute to be added to the model, unless it is a simple type, as determined by BeanUtils#isSimpleProperty in which case it remains unresolved. 如果返回值与以上任何一个不匹配，默认情况下它被视为视图名称，如果它是String或void（通过RequestToViewNameTranslator应用的默认视图名称选择）; 或者作为要添加到模型的模型属性，除非它是一个简单的类型，由BeanUtils＃isSimpleProperty确定，在这种情况下，它仍然未解决。

@返回ModelAndView

controller方法中定义ModelAndView对象并返回，对象中可添加model数据、指定view。

@返回void

在controller方法形参上可以定义request和response，使用request或response指定响应结果：

1、使用request转向页面，如下：

request.getRequestDispatcher("页面路径").forward(request, response);

2、也可以通过response页面重定向：

response.sendRedirect("url")

3、也可以通过response指定响应结果，例如响应json数据如下：

response.setCharacterEncoding("utf-8");

response.setContentType("application/json;charset=utf-8");

response.getWriter().write("json串");

@返回字符串

1，返回void类型，使用response返回

2，使用ResponseBody注解，返回String字符串

3，在类上面加入RestResponse返回String字符串

@RestController

public class TestController {

@RequestMapping("/test.action")

public String test( int ids){

System.out.println("id:"+ids);

return "this is test";

}

@逻辑视图名

controller方法返回字符串可以指定逻辑视图名，通过视图解析器解析为物理视图地址。

//指定逻辑视图名，经过视图解析器解析为jsp物理路径：/WEB-INF/jsp/item/editItem.jsp

return "item/editItem";

@Redirect重定向

Contrller方法返回结果重定向到一个url地址，如下商品修改提交后重定向到商品查询方法，参数无法带到商品查询方法中。

//重定向到queryItem.action地址,request无法带过去

return "redirect:queryItem.action";

redirect方式相当于“response.sendRedirect()”，转发后浏览器的地址栏变为转发后的地址，因为转发即执行了一个新的request和response。

由于新发起一个request原来的参数在转发时就不能传递到下一个url，如果要传参数可以/item/queryItem.action后边加参数，如下：

/item/queryItem?...&…..

对于model设置的值，重定向会拼接到

@forward转发

controller方法执行后继续执行另一个controller方法，如下商品修改提交后转向到商品修改页面，修改商品的id参数可以带到商品修改方法中。

//结果转发到editItem.action，request可以带过去

return "forward:editItem.action";

forward方式相当于“request.getRequestDispatcher().forward(request,response)”，转发后浏览器地址栏还是原来的地址。转发并没有执行新的request和response，而是和转发前的请求共用一个request和response。所以转发前请求的参数在转发后仍然可以读取到。

带域的返回