使用jackson的writeValueAsString把java对象输出成字符串实例，设置应答体的类型

转载地址：http://www.360sdn.com/json/2013/0525/216.html

+http://hw1287789687.iteye.com/blog/2188480

要使用jackson的json解析器需要下载jackson的核心jar包：

jackson-core-2.2.0.jar jackson-core下载地址

jackson-annotations-2.2.0.jar jackson-annotations下载地址

jackson-databind-2.2.0.jar  jackson-databind下载地址

一、首先定义一个java的pojo类,代码如下：

package com;

public class BaseObject {
   private String userName;
   private String userCode;
   private double weight;
   private int height;
   private boolean sex;
   private String[] array;
   private BaseObject  innerObject;
public String getUserName() {
    return userName;
}
public void setUserName(String userName) {
    this .userName = userName;
}
public String getUserCode() {
    return userCode;
}
public void setUserCode(String userCode) {
    this .userCode = userCode;
}
public double getWeight() {
    return weight;
}
public void setWeight( double weight) {
    this .weight = weight;
}
public int getHeight() {
    return height;
}
public void setHeight( int height) {
    this .height = height;
}
public boolean isSex() {
    return sex;
}
public void setSex( boolean sex) {
    this .sex = sex;
}

public BaseObject getInnerObject() {
    return innerObject;
}
public void setInnerObject(BaseObject innerObject) {
    this .innerObject = innerObject;
}
public String[] getArray() {
    return array;
}
public void setArray(String[] array) {
    this .array = array;
}


}

二、把java的pojo类输出成json字符串

使用jackson的ObjectMapper 的writeValueAsString方法可以把pojo类输出成json字符串，代码如下：

package com;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.BaseObject;

public class JacksonJsonTest {
     public static void main(String[] args){
          JacksonJsonTest jsonImple= new JacksonJsonTest();
          try {
          ObjectMapper mapper = new ObjectMapper();
          List dataList= new ArrayList();
          Map map = new HashMap "" >();
            BaseObject object1= new BaseObject();
            object1.setUserName( "张三" );
            object1.setWeight( 65.5 );
            object1.setHeight( 170 );
            object1.setSex( true );
            String[] score={ "80" , "90" , "95" };
            object1.setArray(score);
            BaseObject object2= new BaseObject();
            object2.setUserName( "李四" );
            object2.setWeight( 75.5 );
            object2.setHeight( 171 );
            object2.setSex( true );
            score= new String[ 3 ];
            score[ 0 ]= "65" ;
            score[ 1 ]= "68" ;
            score[ 2 ]= "75" ;
            object2.setArray(score);
            object1.setInnerObject(object2);
            dataList.add(object1);
            map.put( "baseObject" , dataList);
            String json=mapper.writeValueAsString(object1);
            System.out.println(json);

          }
          catch (Exception ex){

          }
      }
}

输出的结果如下：

{"userName":"王五","userCode":null,"weight":65.5,
"height":170,"sex":true,"array":["语文:85",
"数学:80","英语:95"],"innerObject":{"userName":"赵六",
"userCode":null,"weight":75.5,"height":171,"sex":true,
"array":["语文:65","数学:68","英语:75"],"innerObject":null}}

spring MVC中如何设置应答体的content type呢?

spring MVC中如何设置返回类型呢?

我们知道response 的content type主要有:

text/html

text/plain

application/json;charset=UTF-8

application/octet-stream

等

先举一个例子,spring mvc中可以通过如下方式返回json字符串:

Java代码  

1. @ResponseBody  
2.     @RequestMapping(value = "/upload")  
3.     public String upload(HttpServletRequest request, HttpServletResponse response,String contentType2)  
4.             throws IOException {  
5.         String content = null;  
6.         Map map = new HashMap();  
7.         ObjectMapper mapper = new ObjectMapper();  
8.   
9.         map.put("fileName", "a.txt");  
10.         try {  
11.             content = mapper.writeValueAsString(map);  
12.             System.out.println(content);  
13.         } catch (JsonGenerationException e) {  
14.             e.printStackTrace();  
15.         } catch (JsonMappingException e) {  
16.             e.printStackTrace();  
17.         } catch (IOException e) {  
18.             e.printStackTrace();  
19.         }  
20.           
21.         return content;  
22.   
23.     }  

 虽然访问时返回的确实是json字符串,但是response 的content type是"

text/html

"这不是我们期望的,我们期望的response content type是"application/json"或者"application/json;charset=UTF-8",那么如何实现呢?

通过注解@RequestMapping 中的produces

用法如下:

Java代码  

1. @RequestMapping(value = "/upload",produces="application/json;charset=UTF-8")  

 spring MVC官方文档:

Producible Media Types

You can narrow the primary mapping by specifying a list of producible media types. The request will be matched only if the Accept request header matches one of these values. Furthermore, use of the produces condition ensures the actual content type used to generate the response respects the media types specified in the producescondition. For example:

@Controller@RequestMapping(value = "/pets/{petId}", method = RequestMethod.GET, produces="application/json")@ResponseBodypublic Pet getPet(@PathVariable String petId, Model model) {    // implementation omitted}

Just like with consumes, producible media type expressions can be negated as in !text/plain to match to all requests other than those with an Accept header value oftext/plain.

Tip

The produces condition is supported on the type and on the method level. Unlike most other conditions, when used at the type level, method-level producible types override rather than extend type-level producible types.