HttpMessageConverter

HttpMessageConverter是报文请求信息转换器，其提供了将请求信息转换文Java对象以及将Java对象转换为相应信息的方法：

@RequestBody、@ResponseBody、RequestEntity、ResponseEntity

带Request的是将请求转换为Java对象，带Response的是将Java对象转换为相应信息。

RequestBody

@RequestBody注解可以将请求信息赋值给String的形参，例如下面这样的页面的形式

<form th:action="@{/testRequestBody}" method="post"><input type="text" name="username"/><input type="password" name="password"/><input type="submit" name="TestRequestBody"/>
</form>

后台会是这样

    @RequestMapping(value = "/testRequestBody")
//    该形参前的@RequestBody注解会将Request信息注入给形参public String testRequestBody(@RequestBody String RequestBody) {System.out.println(RequestBody);    //username=admin&password=asdasdsa&TestRequestBody=%E6%8F%90%E4%BA%A4return "success";}

RequestEntity

RequestEntity是一个类，也可以获取参数信息（请求头和请求体）

    @RequestMapping(value = "/testRequestEntity")public String testRequestEntity(RequestEntity<String> requestEntity) {System.out.println(requestEntity.getHeaders());     //获取请求头     [host:"localhost:8080", connection:"keep-alive", content-length:"63", cache-control:"max-age=0", sec-ch-ua:""Chromium";v="112", "Google Chrome";v="112", "Not:A-Brand";v="99"", sec-ch-ua-mobile:"?0", sec-ch-ua-platform:""Windows"", upgrade-insecure-requests:"1", origin:"http://localhost:8080", user-agent:"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/112.0.0.0 Safari/537.36", accept:"text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7", sec-fetch-site:"same-origin", sec-fetch-mode:"navigate", sec-fetch-user:"?1", sec-fetch-dest:"document", referer:"http://localhost:8080/springMVC/", accept-encoding:"gzip, deflate, br", accept-language:"en-US,en;q=0.9,zh-CN;q=0.8,zh;q=0.7", cookie:"Idea-cd4fc388=5f928943-4086-4741-8f67-92fff7302594", Content-Type:"application/x-www-form-urlencoded;charset=UTF-8"]System.out.println(requestEntity.getBody());        //获取请求体     username=admin&password=1111&TestRequestBody=%E6%8F%90%E4%BA%A4return "success";}

ResponseBody

@ResponseBody注解会将返回值作为返回体进行返回，例如下面代码

    @RequestMapping(value="/testResponseBody")@ResponseBodypublic String testResponseBody() {return "failure";}

就会将failure作为字符串显示在页面上，而不加该注解则会由Thymeleaf解析显示该显示的页面

导入json的必要依赖

<!--        json的必要依赖--><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.12.1</version></dependency>

json是一种javascript的数据交换格式

    @RequestMapping ("/testResponseUser")@ResponseBodypublic User testResponseUser() {//如果将对象作为返回值，则json会自动将对象自动转换为String类型的字符串//json数组return new User(1001, "Lili", "1999", "女", 24);}

使用Ajax进行response

Ajax默认是不进行跳转的请求，可以方便的实现很多功能

<div id="app"><a @click="testAxios" th:href="@{/testAxios}">SpringMVC处理Ajax</a>
</div><script type="text/javascript" th:src="@{/static/js/vue.js}"></script>
<script type="text/javascript" th:src="@{/static/js/axios.min.js}"></script>
<script type="text/javascript">new Vue({"el" : "#app",methods : {testAxios : function (event) {//使用ajax发送请求axios({//post请求method : "post",url : event.target.href,params : {username : "admin",password : "123456"}}).then(function(response){alert(response.data);});event.preventDefault();}}})
</script>