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 + "]";
     }

 }