SpringMVC @Controller和@RestController注解的区别

小鱼儿 2022-02-04 08:13 300阅读 0赞

**官方文档：**

@RestController is a stereotype annotation that combines @ResponseBody and @Controller.

意思是： @RestController注解相当于@ResponseBody ＋ @Controller合在一起的作用。

### 1 如果只是使用@RestController注解Controller ###

Controller中的方法无法返回jsp页面，或者html，配置的视图解析器 InternalResourceViewResolver不起作用，返回的内容就是Return 里的内容（String/JSON）。

### 2 如果只是使用@Controller注解Controller ###

若需要返回到指定页面，则需要用 @Controller配合视图解析器InternalResourceViewResolver才行。

若需要返回JSON，XML或自定义mediaType内容到页面，则需要在对应的方法上加上@ResponseBody注解。

### 3、实例： ###

<bean id="" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
 		<property name="prefix" value="/WEB-INF/view/"></property>
 		<property name="suffix" value=".jsp"></property>
 	</bean>

**1）使用@Controller 注解Controller**

若返回到指定页面，在对应的方法上，视图解析器可以解析return 的jsp,html页面，并且跳转到相应页面。即返回 login.jsp 到页面。

@Controller
    public class LogincController {	
    
    	@RequestMapping(value="/login",method = RequestMethod.GET)
    	public String login() {
    	    return "login";
    	}
    }

若返回 json 等内容到页面，则需要加@ResponseBody注解。即返回 login 到页面

@Controller
    public class LogincController {	
    
            @ResponseBody
    	@RequestMapping(value="/login",method = RequestMethod.GET)
    	public String login() {
    	    return "login";
    	}
    }

**2）使用@RestController注解Controller**

相当于@Controller+@ResponseBody两个注解的结合，返回json数据不需要在方法前面加@ResponseBody注解了，但使用@RestController这个注解，就不能返回jsp,html页面，视图解析器无法解析jsp,html页面。即返回 login 到页面

@RestController
    public class LogincController {	
    
    	@RequestMapping(value="/login",method = RequestMethod.GET)
    	public String login() {
    	    return "login";
    	}
    }

如果想返回指定页面，通过 ModelAndView 返回，亲测有效（不推荐）

@RestController
    public class LogincController {
    	
    	@RequestMapping(value="/login",method = RequestMethod.GET)
    	public ModelAndView login() {
    		ModelAndView mv = new ModelAndView();
    		mv.setViewName("login");
    		return mv;
    	}
    }

最后贴上 Spring5.x 的 @RestController 和 @Controller 源码，加深学习和理解。

**Controller源码：**

/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
 package org.springframework.stereotype;
 
 import java.lang.annotation.Documented;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 import org.springframework.core.annotation.AliasFor;
 
 /**
 * Indicates that an annotated class is a "Controller" (e.g. a web controller).
 *
 * This annotation serves as a specialization of {@link Component @Component},
 * allowing for implementation classes to be autodetected through classpath scanning.
 * It is typically used in combination with annotated handler methods based on the
 * {@link org.springframework.web.bind.annotation.RequestMapping} annotation.
 *
 * @author Arjen Poutsma
 * @author Juergen Hoeller
 * @since 2.5
 * @see Component
 * @see org.springframework.web.bind.annotation.RequestMapping
 * @see org.springframework.context.annotation.ClassPathBeanDefinitionScanner
 */
 @Target({ElementType.TYPE})
 @Retention(RetentionPolicy.RUNTIME)
 @Documented
 @Component
 public @interface Controller {
 
 	/**
 	 * The value may indicate a suggestion for a logical component name,
 	 * to be turned into a Spring bean in case of an autodetected component.
 	 * @return the suggested component name, if any (or empty String otherwise)
 	 */
 	@AliasFor(annotation = Component.class)
 	String value() default "";
 
 }

**RestController源码：**

/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
 package org.springframework.web.bind.annotation;
 
 import java.lang.annotation.Documented;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 import org.springframework.core.annotation.AliasFor;
 import org.springframework.stereotype.Controller;
 
 /**
 * A convenience annotation that is itself annotated with
 * {@link Controller @Controller} and {@link ResponseBody @ResponseBody}.
 * 
 * Types that carry this annotation are treated as controllers where
 * {@link RequestMapping @RequestMapping} methods assume
 * {@link ResponseBody @ResponseBody} semantics by default.
 *
 * NOTE: {@code @RestController} is processed if an appropriate
 * {@code HandlerMapping}-{@code HandlerAdapter} pair is configured such as the
 * {@code RequestMappingHandlerMapping}-{@code RequestMappingHandlerAdapter}
 * pair which are the default in the MVC Java config and the MVC namespace.
 *
 * @author Rossen Stoyanchev
 * @author Sam Brannen
 * @since 4.0
 */
 @Target(ElementType.TYPE)
 @Retention(RetentionPolicy.RUNTIME)
 @Documented
 @Controller
 @ResponseBody
 public @interface RestController {
 
 	/**
 	 * The value may indicate a suggestion for a logical component name,
 	 * to be turned into a Spring bean in case of an autodetected component.
 	 * @return the suggested component name, if any (or empty String otherwise)
 	 * @since 4.0.1
 	 */
 	@AliasFor(annotation = Controller.class)
 	String value() default "";
 
 }

**ResponseBody源码：**

@Target({ElementType.TYPE, ElementType.METHOD})
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    public @interface ResponseBody {
    
    }

end ~