SpringMVC之响应

返回字符串

返回字符串相当于返回视图名称，该视图名称经过视图解析器得到视图路径

@RequestMapping("/testString")
public String testString() {
    System.out.println("testString()执行");
    return "success";
}

返回void

默认行为：以方法名作为视图名称，经过视图解析器得到视图路径

@RequestMapping("/testVoid1")
public void testVoid1() {
    System.out.println("testVoid1()执行");
}

通过HttpServletRequest请求转发，转发地址不走视图解析器：

@RequestMapping("/testVoid2")
public void testVoid2(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    System.out.println("testVoid2()执行");
    req.getRequestDispatcher("/WEB-INF/pages/success.jsp").forward(req, resp);
}

通过HttpServletResponse重定向

@RequestMapping("/testVoid3")
public void testVoid3(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    System.out.println("testVoid3()执行");
//    resp.sendRedirect("testVoid2");
    resp.sendRedirect("/springmvc03/test1/testVoid2");
}

通过Response对象指定响应结果

@RequestMapping("/testVoid4")
public void testVoid4(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    System.out.println("testVoid4()执行");
    resp.setCharacterEncoding("UTF-8");
    resp.setContentType("text/html;charset=UTF-8");
    resp.getWriter().write("testVoid4");
}

返回ModelAndView

addObject(String, @Nullable Object)：变量赋值，在jsp页面中通过requestScope取值
setViewName(String)：设置视图名称

@RequestMapping("/testModelAndView")
public ModelAndView testModelAndView() {
    ModelAndView modelAndView = new ModelAndView();
    modelAndView.addObject("username", "张三");
    modelAndView.setViewName("testModelAndView");
    return modelAndView;
}

请求转发

@RequestMapping("/testForward")
public String testForward() {
    System.out.println("testForward()执行");
    return "forward:/WEB-INF/pages/success.jsp";
}

重定向

@RequestMapping("/testRedirect")
public String testRedirect() {
    System.out.println("testRedirect()执行");
    return "redirect:testString";
}

返回json

导入jackson类库：

<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
  <artifactId>jackson-databind</artifactId>
  <version>2.12.2</version>
</dependency>
<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
  <artifactId>jackson-core</artifactId>
  <version>2.12.2</version>
</dependency>
<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
  <artifactId>jackson-annotations</artifactId>
  <version>2.12.2</version>
</dependency>

@RequestMapping("/testJson")
public @ResponseBody User testJson(@RequestBody User user) {
    System.out.println("testJson()执行");
    System.out.println(user);
    user.setUsername("张三丰");
    return user;
}