三、数据响应

一、SpringMVC的数据响应方式

1. 页面跳转

   • 直接返回字符串

   • 通过ModelAndView对象返回

2. 回写数据

   • 直接返回字符串
   • 返回对象或集合

1、页面跳转

（1）返回字符串形式

直接返回字符串：此种方式会将返回的字符串与视图解析器的前后缀拼接后跳转

未传参

@Controller
@RequestMapping("/user")
public class UserController {

    @RequestMapping("/quick1")
    public String stringTest1(){
        return "quick1";
    }
}

传参

@Controller
@RequestMapping("/user")
public class UserController {

    @RequestMapping("/quick2")
	public String stringTest2(Model model){
        model.addAttribute("username","胡二狗quick2");
    	return "quick2";
	}
}

使用request域存放数据

@Controller
@RequestMapping("/user")
public class UserController {

     @RequestMapping("/quick3")
 	 public String stringTest2(HttpServletRequest request) {
     	request.setAttribute("username", "胡二狗quick3");
      	return "quick3";
	 }
}

spring-mvc.xml

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

最终转发资源地址：/WEB-INF/views/index.jsp

信息

转发：forward:/WEB-INE/views/index.jsp

重定向：redirect:/index.jsp

（2）返回ModelAndView对象

手动创建ModelAndView

@Controller
@RequestMapping("/user")
public class UserController {
    
	@RequestMapping("/quick3")
	public ModelAndView modelAndViewTest1(){
	    ModelAndView modelAndView = new ModelAndView();
	    modelAndView.addObject("username","胡二狗quick3");
	    modelAndView.setViewName("quick2");
	    return modelAndView;
    }
}

自动创建MOdelAndView

@Controller
@RequestMapping("/user")
public class UserController {
    
	@RequestMapping("/quick3")
	public ModelAndView modelAndViewTest2(ModelAndView modelAndView){
	    modelAndView.addObject("username","胡二狗quick4");
	    modelAndView.setViewName("quick4");
	    return modelAndView;
    }
}

spring-mvc.xml

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

2、回写数据

（1）直接返回字符串

• 利用response回写数据

  @RequestMapping("/huixie1")
  public void HuiXieDataTest1(HttpServletResponse response) throws IOException {
      //解决乱码
      response.setContentType("text/html;charset=utf-8");
      response.getWriter().print("利用response回写数据");
  }

• 利用@Response注解回写数据

  @RequestMapping(value = "/huixie2",produces = "text/html;charset=utf-8")  //解决中文乱码
  @ResponseBody
  public String HuiXieDataTest2()  {
      return "利用@ResponseBody回写数据";
  }

（2）直接返回对象或集合

• 手动返回字符串json数据

  @RequestMapping(value = "/huixie3",produces = "text/html;charset=utf-8")
  @ResponseBody
  public String HuiXieDataTest3(){
      return "{\"username\":\"胡二狗\",\"age\":\"13\"}";
  }

• 导入json工具自动转化json数据

  工具类坐标

  一键复制

   <dependency>
       <groupId>com.fasterxml.jackson.core</groupId>
       <artifactId>jackson-core</artifactId>
       <version>2.15.4</version>
   </dependency>
  
   <dependency>
       <groupId>com.fasterxml.jackson.core</groupId>
       <artifactId>jackson-databind</artifactId>
       <version>2.15.4</version>
   </dependency>
  
   <dependency>
       <groupId>com.fasterxml.jackson.core</groupId>
       <artifactId>jackson-annotations</artifactId>
       <version>2.15.4</version>
   </dependency>

  jackson-core

   <dependency>
       <groupId>com.fasterxml.jackson.core</groupId>
       <artifactId>jackson-core</artifactId>
       <version>2.15.4</version>
   </dependency>

  jackson-databind

  <dependency>
       <groupId>com.fasterxml.jackson.core</groupId>
       <artifactId>jackson-databind</artifactId>
       <version>2.15.4</version>
  </dependency>

  jackson-annotations

  <dependency>
       <groupId>com.fasterxml.jackson.core</groupId>
       <artifactId>jackson-annotations</artifactId>
       <version>2.15.4</version>
  </dependency>

  测试

  @RequestMapping(value = "/huixie4",produces = "text/html;charset=utf-8")
  @ResponseBody
  public String HuiXieDataTest4() throws JsonProcessingException {
      User user=new User(1,"胡二狗",21);
      
      ObjectMapper objectMapper=new ObjectMapper();
      String json = objectMapper.writeValueAsString(user);
  
      return json;
  }

• SpringMVC使用适配器返回json数据

  在spring-mvc.xml文件配置适配器

  <!-- 配置处理器映射器-->
  <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
      <property name="messageConverters">
          <list>
              <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"/>
          </list>
      </property>
  </bean>

  测试

  @RequestMapping(value = "/huixie5")
  @ResponseBody
  public User HuiXieDataTest5()  {
      User user=new User(1,"胡二狗",21);
      return user;
  }

  警告

  使用适配器后，原先加上@ResponseBody注解返回出的字符串会经过jackson的转化，但肯定转化会失败，所以会报错

  使用MVC命名空间简写

  <?xml version="1.0" encoding="UTF-8"?>
  <beans xmlns="http://www.springframework.org/schema/beans"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns:context="http://www.springframework.org/schema/context"
         xsi:schemaLocation="
         http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
         http://www.springframework.org/schema/context  http://www.springframework.org/schema/context/spring-context.xsd
  ">
      <context:component-scan base-package="com.hdq.controller"/>
  
      <mvc:annotation-driven/>
  
  </beans>