处理器方法的返回值

1.1 返回ModelAndView

@RequestMapping("/func1.action")
public ModelAndView func1() {
    System.out.println("func1..");
    ModelAndView modelAndView = new ModelAndView();
    modelAndView.setViewName("index02.jsp");
    modelAndView.addObject("username", "admin");
    modelAndView.addObject("age", 18);
    return modelAndView;
}

1.2 返回String

/**
     * 返回值String其实是视图的名称,在Model中可以设置数据
     * @param model
     * @return
     */
@RequestMapping("/func1.action")
public String func1(Model model) {
    System.out.println("func1..");
    model.addAttribute("age",18);
    return "index02.jsp";
}

1.3 返回对象

<?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"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       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
                           http://www.springframework.org/schema/mvc
                           http://www.springframework.org/schema/mvc/spring-mvc.xsd">
    <mvc:annotation-driven/>
    <!--配置注解扫描器-->
    <context:component-scan base-package="com.it.bigdata"/>
    <!--处理器映射器-->
    <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping"></bean>
    <!--处理器适配器-->
    <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter"></bean>
    <!--视图解析器-->
    <!--    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
            <property name="suffix" value=".jsp"></property>
        </bean>-->
</beans>



<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.9.6</version>
</dependency>



@RequestMapping("/func1.action")
@ResponseBody
public User func1() throws IOException {
    User user = new User();
    user.setName("小花");
    user.setAge(20);
    return user;//把对象转换成json字符串进行返回了
}

1.4 返回void

@RequestMapping("/func1.action")
public void func1(Model model, HttpServletRequest request, HttpServletResponse resp) throws IOException {
    System.out.println("func1..");
    User user = new User();
    user.setName("小花");
    user.setAge(20);
    System.out.println(request.getParameter("id"));
    resp.getWriter().write("hello");
}

1.5 处理器的参数

• 可以直接以参数名字当做形参
  @RequestMapping("/func1.action")
  public void func1( Integer id) throws IOException {
  System.out.println(“func1…”);
  System.out.println(id);
  }

• 可以和形参不一致(不建议使用)
  @RequestMapping("/func1.action")
  public void func1(@RequestParam(“id”) Integer idd) throws IOException {
  System.out.println(“func1…”);
  System.out.println(idd);
  }

• 使用request获取参数
  @RequestMapping("/func1.action")
  public void func1(Model model, HttpServletRequest request, HttpServletResponse resp) throws IOException {
  System.out.println(request.getParameter(“id”));
  }

• 把参数直接包装成对象
  @RequestMapping("/func1.action")
  @ResponseBody
  public User func1(User user) throws IOException {
  System.out.println(user);
  return user;
  }

1.6. 返回Json对象

• 返回对象的做法
• 自己使用fastjson或者其他转换json的工具实现
  @RequestMapping("/func1.action")
  @ResponseBody
  public String func1(User user) throws IOException {
  System.out.println(user);
  return JSON.toJSONString(user);
  }