Jackson 高性能的JSON处理 ObjectMapper

http://blog.csdn.net/wangyang2698341/article/details/8223929

今天自行研究了下json ，感觉非常好用，经过测试比google的GSON快多了

      同时Jackson可以轻松的将Java对象转换成json对象和xml文档，同样也可以将json、xml转换成Java对象。功能非常的强悍！

       大家也知道，json 在如今互联网时代应用的非常广，因为大家如此的关注，所以对json的解析性能要求也是非常高的。

一、 准备工作

1、 下载依赖库jar包

Jackson的jar all下载地址：http://jackson.codehaus.org/1.7.6/jackson-all-1.7.6.jar

然后在工程中导入这个jar包即可开始工作

官方示例：http://wiki.fasterxml.com/JacksonInFiveMinutes

因为下面的程序是用junit测试用例运行的，所以还得添加junit的jar包。版本是junit-4.2.8

如果你需要转换xml，那么还需要stax2-api.jar

2、 测试类基本代码如下

package jackJson.test;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import jackJson.test.pojo.Student;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationConfig;

public class Jackson {
    
    public  static JsonGenerator jsonGenerator = null;  
    private static ObjectMapper mapper = new ObjectMapper();  
    
    public static void main(String[] args) {  
        Student student = new Student();  
        student.setIsstudent(true);  
        student.setUid(1000);  
        student.setUname("xiao liao");
        student.setUpwd("123");  
        student.setNumber(12);  
          
        Map<String, Student> stuMap = new HashMap<String, Student>();  
        stuMap.put("1", student);  
        stuMap.put("2", student);  
          
        List<Object> stuList = new ArrayList<Object>();  
        List<Student> stuList1 = new ArrayList<Student>();  
        stuList1.add(student);  
        student=  new  Student();  
        student.setIsstudent(false);  
        student.setUid(200);  
        student.setUname("xiao mi");  
        stuList1.add(student);  
          
        stuList.add(student);  
        stuList.add("xiao xin");  
        stuList.add("xiao er");  
        stuList.add(stuMap);  
      //  readJson2List(); 
      //  readJson2Array();
        try {  
              
            //writeArray2Json(array);  
            writeJson2List();  
            //writeEntity2Json(student);  
            //writeJson2Entity();  
            //writeMap2Json(stuMap);  
            //writeList2Json(stuList1);  
              
        } catch (IOException e) {  
            e.printStackTrace();  
        }
    }  
     /** 
      *  
      * <code>writeEntity2Json</code> 
      * @description: TODO(实体类转换成json)  
      * @param object 
      * @throws IOException 
      * @since   2011-11-8     廖益平 
      */  
     public static void writeEntity2Json(Object object) throws IOException {  
           mapper.writeValue( new File("D:\developSoft\aaadowload\testjson1\lib\aa.txt"),object );  
           mapper.writeValue( System.out,object );  
           
     }  
     /** 
      *  
      * <code>writeArray2Json</code> 
      * @description: TODO(数组转换成json数组)  
      * @param object 
      * @throws IOException 
      * @since   2011-11-8     廖益平 
      */  
     public static void writeArray2Json(Object object) throws IOException {  
           
         // writeValue具有和writeObject相同的功能  
         mapper.writeValue( new File("D:\developSoft\aaadowload\testjson1\lib\aa.txt"),object );  
         mapper.writeValue(System.out,object );  
           
     }  
     /** 
      *  
      * <code>writeMap2Json</code> 
      * @description: TODO(map对象转换成json对象)  
      * @param object 
      * @throws IOException 
      * @since   2011-11-8     廖益平 
      */  
     public static void writeMap2Json(Object object) throws IOException {  
           
         System.out.println("使用ObjectMapper-----------");  
         // writeValue具有和writeObject相同的功能  
         System.out.println("==>"+mapper.writeValueAsString(object));  
         mapper.writeValue( new File("D:\developSoft\aaadowload\testjson1\lib\aamap.txt"),object );  
         mapper.writeValue( System.out , object );  
     }  
     /** 
      *  
      * <code>writeList2Json</code> 
      * @description: TODO(list转换成json)  
      * @param object 
      * @throws IOException 
      * @since   2011-11-8     廖益平 
      */  
     public static void writeList2Json(Object object) throws IOException {  
         System.out.println("==>"+mapper.writeValueAsString(object));  
         mapper.writeValue( new File("D:\developSoft\aaadowload\testjson1\lib\aamap.txt"),object );  
         mapper.writeValue( System.out , object );  
     }  
     /** 
      *  
      * <code>writeJson2Entity</code> 
      * @description: TODO(json转换成实体)  
      * @throws IOException 
      * @since   2011-11-8     廖益平 
      */  
     public static void writeJson2Entity() throws IOException {  
         System.out.println("json串转换成entity-------------");  
//       File file = new File("D:\developSoft\aaadowload\testjson1\lib\aa.txt");  
//       FileInputStream inputStream = new FileInputStream(file);  
//       Student student = mapper.readValue(inputStream,Student.class);  
//       System.out.println(student.toString());  
         //漂亮输出  
         //mapper.defaultPrettyPrintingWriter().writeValueAsString(value);  
      
         String json = "{"uid":1000,"uname":"xiao liao","upwd":"123","number":12.0,"isstudent":true}";  
         Student student1 = mapper.readValue(json,Student.class);  
         System.out.println("json2:"+student1.toString());  
     }  
     /** 
      *  
      * <code>writeJson2List</code> 
      * @description: TODO(json专程list对象)  
      * @throws IOException 
      * @since   2011-11-8     廖益平 
      */  
     public static void writeJson2List() throws IOException {  
         System.out.println("json串转换成entity-------------");  
         File file = new File("D:\developSoft\aaadowload\testjson1\lib\aa.txt");  
         FileInputStream inputStream = new FileInputStream(file);  
         Student student = mapper.readValue(inputStream,Student.class);  
         System.out.println(student.toString());  
           
         String json = "[{"uid":1000,"uname":"xiao liao","upwd":"123","number":12.0,"isstudent":true},{"uid":200,"uname":"xiao mi","upwd":null,"number":0.0,"isstudent":false}]";  
         List<LinkedHashMap<String, Object>> s= mapper.readValue(json,List.class);  
         for (int i = 0; i < s.size(); i++) {  
             LinkedHashMap<String, Object> link = s.get(i);  
             Set<String>  key = link.keySet();  
             for (Iterator iterator = key.iterator(); iterator.hasNext();) {  
                String string = (String) iterator.next();  
                System.out.println(string+"==>"+link.get(string));  
                  
            }  
             System.out.println("json:"+i+""+s.get(i).toString());  
              
        }  
     }  
     /** 
       * JSON转换为List对象 
       */  
      public static void readJson2List() {  
           String json = "[{"uid":1,"uname":"www","number":234,"upwd":"456"},"  
             + "{"uid":5,"uname":"tom","number":3.44,"upwd":"123"}]";  
           try {  
                List<LinkedHashMap<String, Object>> list = mapper.readValue(json, List.class); 
                System.out.println(list.size());  
                for (int i = 0; i < list.size(); i++) {  
                     Map<String, Object> map = list.get(i);  
                     Set<String> set = map.keySet();  
                     for (Iterator<String> it = set.iterator(); it.hasNext();) {  
                          String key = it.next();  
                          System.out.println(key + ":" + map.get(key));  
                     }  
                }  
           } catch (JsonParseException e) {  
               e.printStackTrace();  
           } catch (JsonMappingException e) {  
               e.printStackTrace();  
           } catch (IOException e) {  
               e.printStackTrace();  
           }  
      }  
      /** 
       * JSON转换为List对象 
       */  
      public static void readJson2Array() {  
          String json = "[{"uid":1,"uname":"www","number":234,"upwd":"456"},"  
              + "{"uid":5,"uname":"tom","number":3.44,"upwd":"123"}]";  
          try {  
              Student[] students = mapper.readValue(json, Student[].class);  
              for (Student student : students) {  
                System.out.println(">"+student.toString());  
            }  
          } catch (JsonParseException e) {  
              e.printStackTrace();  
          } catch (JsonMappingException e) {  
              e.printStackTrace();  
          } catch (IOException e) {  
              e.printStackTrace();  
          }  
      }  
  

}

package jackJson.test.pojo;

public class Student {
    
    private Integer uid;
    private String uname;
    private String upwd;
    private Integer number;
    private Boolean isstudent;
    public Integer getUid() {
        return uid;
    }
    public void setUid(Integer uid) {
        this.uid = uid;
    }
    public String getUname() {
        return uname;
    }
    public void setUname(String uname) {
        this.uname = uname;
    }
    public String getUpwd() {
        return upwd;
    }
    public void setUpwd(String upwd) {
        this.upwd = upwd;
    }
    public Integer getNumber() {
        return number;
    }
    public void setNumber(Integer number) {
        this.number = number;
    }
    public Boolean getIsstudent() {
        return isstudent;
    }
    public void setIsstudent(Boolean isstudent) {
        this.isstudent = isstudent;
    }
    @Override
    public String toString() {
        return "Student [uid=" + uid + ", uname=" + uname + ", upwd=" + upwd
                + ", number=" + number + ", isstudent=" + isstudent + "]";
    }

}