springMvc注解之@ResponseBody和@RequestBody

简介

springmvc对json的前后台传输做了很好封装，避免了重复编码的过程，下面来看看常用的@ResponseBody和@RequestBody注解

添加依赖

springmvc对json的处理依赖jackson

<dependency>
    <groupId>org.codehaus.jackson</groupId>
    <artifactId>jackson-core-asl</artifactId>
    <version>1.9.11</version>
</dependency>
<dependency>
    <groupId>org.codehaus.jackson</groupId>
    <artifactId>jackson-mapper-asl</artifactId>
    <version>1.9.11</version>
</dependency>      

xml配置

<mvc:annotation-driven />//不要忘了命名空间配置      

@ResponseBody

如果传输的是单层json对象，我们后台可以直接用 @RequestParam接收

$.ajax({
    type : "post",
    dataType : "json",
    url : "/testRequestBody",
    data:{
        name:"韦德",
        age:35
    },
    success : function(result) {
    }
});      

@RequestMapping("/testRequestBody")
public String testRequestBody(@RequestParam Map<String, Object> map) {
  System.out.println(map);// {name=韦德, age=35}
  return "index";
}      

如果传输的是多层嵌套json对象，这个时候会就会出现数据丢失问题

@ResponseBody很好的解决了这个问题，它会把前台传输过来的json转化为后台对应的对象

$.ajax({
    type : "post",
    dataType : "json",
    url : "/testRequestBody",
    contentType:"application/json",   
    data:JSON.stringify({
        name:"韦德",
        win:[2006,2012,2013],
        age:35
    }),
    success : function(result) {
    }
});      

@RequestMapping("/testRequestBody")
public String testRequestBody(@RequestBody Map<String, Object> map) {
  System.out.println(map);//{name=韦德, win=[2006, 2012, 2013], age=35}
  return "index";
}      

需要注意的是前台需要指定contentType为"application/json"

同时要把json对象转化为String，否则后台不能识别

ajax请求返回json格式，往常我们可以这样做

private void writeJson(HttpServletResponse response, Object object) {
  String json = JSON.toJSONString(object);
  response.setCharacterEncoding("UTF-8");
  response.setContentType("application/json; charset=utf-8");
  PrintWriter out = null;
  try {
    out = response.getWriter();
    out.write(json);
  } catch (IOException e) {
    e.printStackTrace();
  } finally {
    if (out != null) {
      out.close();
    }
  }
}      

这个时候 @ResponseBody就派上用场了，只需要一个注解，全部搞定

$.ajax({
    type : "post",
    dataType : "json",
    url : "/testResponseBody",
    success : function(result) {
        console.info(result);
    }
});      

@RequestMapping("/testResponseBody")
@ResponseBody
public Map<String, Object> testRequestBody() {
  Map<String, Object> result = new HashMap<String, Object>();
  result.put("name", "韦德");
  result.put("age", 35);
  return result;
}      

前台console输出

{
    "age": 35,
    "name": "韦德"
}      

总结

在网上看到很不错的流程图，作为总结吧

<dependency>
    <groupId>org.codehaus.jackson</groupId>
    <artifactId>jackson-core-asl</artifactId>
    <version>1.9.11</version>
</dependency>
<dependency>
    <groupId>org.codehaus.jackson</groupId>
    <artifactId>jackson-mapper-asl</artifactId>
    <version>1.9.11</version>
</dependency>      

<mvc:annotation-driven />//不要忘了命名空间配置      

$.ajax({
    type : "post",
    dataType : "json",
    url : "/testRequestBody",
    data:{
        name:"韦德",
        age:35
    },
    success : function(result) {
    }
});      

@RequestMapping("/testRequestBody")
public String testRequestBody(@RequestParam Map<String, Object> map) {
  System.out.println(map);// {name=韦德, age=35}
  return "index";
}      

$.ajax({
    type : "post",
    dataType : "json",
    url : "/testRequestBody",
    contentType:"application/json",   
    data:JSON.stringify({
        name:"韦德",
        win:[2006,2012,2013],
        age:35
    }),
    success : function(result) {
    }
});      

@RequestMapping("/testRequestBody")
public String testRequestBody(@RequestBody Map<String, Object> map) {
  System.out.println(map);//{name=韦德, win=[2006, 2012, 2013], age=35}
  return "index";
}      

private void writeJson(HttpServletResponse response, Object object) {
  String json = JSON.toJSONString(object);
  response.setCharacterEncoding("UTF-8");
  response.setContentType("application/json; charset=utf-8");
  PrintWriter out = null;
  try {
    out = response.getWriter();
    out.write(json);
  } catch (IOException e) {
    e.printStackTrace();
  } finally {
    if (out != null) {
      out.close();
    }
  }
}      

$.ajax({
    type : "post",
    dataType : "json",
    url : "/testResponseBody",
    success : function(result) {
        console.info(result);
    }
});      

@RequestMapping("/testResponseBody")
@ResponseBody
public Map<String, Object> testRequestBody() {
  Map<String, Object> result = new HashMap<String, Object>();
  result.put("name", "韦德");
  result.put("age", 35);
  return result;
}      

{
    "age": 35,
    "name": "韦德"
}