java解析和读取JSON

1.JSON介绍

　　JSON比XML简单，主要体现在传输相同信息的情况下，文件的大小不同。

　　JSON只用于传输信息，XML还可以用于配置文件的使用。

　　JSON中的符号主要有： " , [ {:

2.JSON中的数组和对象

　　2.1数组（JSONArray）

　　数组用一对[]，表示存放的是一般的数组数据。

　　如：["11","22","33"]，表示这是一个JSONArray数组，里面有3个数据：”11“，”22“，”33“。当然可以是复杂的数据，就是所谓的嵌套定义吧。

　　2.对象（JSONObject）

　　对象用一对{}，来表示其中JSON通用的”键-值“对。

　　如：{"sex1":"female","name0":"zhangsan"}，表示的是一个JSON对象，里面有两组数据(键值对)，sex1=female，name0=zhangsan。当然这里键对应的数据值，可以是复杂的JSON对象或者数组。

3.代码示例

 package com.somnus.json;

 import java.lang.reflect.Field;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;

 import net.sf.json.JSONArray;
 import net.sf.json.JSONObject;
 import net.sf.json.JsonConfig;
 import net.sf.json.processors.JsDateJsonValueProcessor;
 import net.sf.json.util.CycleDetectionStrategy;

 /**
  * Json与javaBean之间的转换工具类
  *
  * @author
  *
  *         {@code   现使用json-lib组件实现
  *          需要
  *              json-lib-2.4-jdk15.jar
  *              ezmorph-1.0.6.jar
  *              commons-collections-3.1.jar
  *              commons-lang-2.0.jar
  *              commons-beanutils-1.9.1.jar
  *          支持
  * }
  */

 public class JsonUtil {
     // *************************************以下对象转换为JSON***************************************************************
     private static JsonConfig configJson(String[] excludes) {
         JsonConfig jsonConfig = new JsonConfig();
         jsonConfig.setExcludes(excludes);
         jsonConfig.setIgnoreDefaultExcludes(false);
         jsonConfig.setCycleDetectionStrategy(CycleDetectionStrategy.LENIENT);
         jsonConfig.registerJsonValueProcessor(Date.class, new JsDateJsonValueProcessor());
         return jsonConfig;
     }

     /**
      * 将java对象转换成json字符串
      *
      * @param bean
      * @return
      */
     public static String obj2JsonString(Object obj) {
         JSONObject json = JSONObject.fromObject(obj);
         return json.toString();
     }

     /**
      * 将java对象指定的属性转换成json字符串
      *
      * @param bean
      * @param include
      *            包含的属性字段值
      * @param nory
      * @return
      */
     public static String obj2JsonString(Object obj, String[] include, boolean nory) {
         JSONObject json = null;
         // 转换include里的属性
         if (nory){
             Field[] fields = obj.getClass().getDeclaredFields();
             String str = "";
             for (Field field : fields) {
                 str += ("#" + field.getName());
             }
             fields = obj.getClass().getSuperclass().getDeclaredFields();
             for (Field field : fields) {
                 str += ("#" + field.getName());
             }
             str += "#";
             for (String s : include) {
                 str = str.replace("#" + s + "#", "#");
             }
             json = JSONObject.fromObject(obj, configJson(str.split(":")));
         }
         // 转换除了include里的属性
         else {
             json = JSONObject.fromObject(obj, configJson(include));
         }
         return json.toString();
     }

     /**
      * 将java对象List集合转换成json字符串
      *
      * @param beans
      * @return
      */
     public static <E> String list2JsonString(List<E> list) {
         StringBuffer temp = new StringBuffer();
         temp.append("[");
         int size = list.size();
         for (int i = 0; i < size; i++) {
             temp.append(obj2JsonString(list.get(i)) + ((i < size - 1) ? "," : ""));
         }
         temp.append("]");
         return temp.toString();
     }

     public static <E> String list2JsonString_(List<E> list) {
         JSONArray jsonArray = JSONArray.fromObject(list);
         return jsonArray.toString();
     }


     /**
      * 将List中所含对象指定的属性转换成json字符串
      *
      * @param bean
      * @param include
      *            包含的属性字段值
      * @param nory
      * @return
      */
     public static <E> String list2JsonString(List<E> beans, String[] include, boolean nory) {
         StringBuffer rest = new StringBuffer();
         rest.append("[");
         int size = beans.size();
         for (int i = 0; i < size; i++) {
             rest.append(obj2JsonString(beans.get(i), include, nory) + ((i < size - 1) ? "," : ""));
         }
         rest.append("]");
         return rest.toString();
     }


     /**
      * map集合转换成json格式数据
      *
      * @param map
      * @return
      */
     @SuppressWarnings("unchecked")
     public static <E, V> String map2JsonString(Map<E, V> map, String[] include, boolean nory) {
         String s_json = "{";
         for (Iterator<E> it = map.keySet().iterator(); it.hasNext();) {
             String key = (String) it.next();
             if (map.get(key) == null) {
             } else if (map.get(key) instanceof List) {
                 s_json += ("\"" + key + "\":" + JsonUtil.list2JsonString((List<E>) map.get(key), include, nory));
             } else {
                 JSONObject json = JSONObject.fromObject(map.get(key));
                 s_json += ("\"" + key + "\":" + json.toString());
             }
             if (it.hasNext()) {
                 s_json += ",";
             }
         }
         s_json += "}";
         return s_json;
     }

     // *************************************以下JSON转换为对象***************************************************************

     /**
      * 从一个JSON 对象字符格式中得到一个java对象
      *
      * @param jsonString
      * @param beanCalss
      * @return
      */
     @SuppressWarnings("unchecked")
     public static <T> T jsonString2Object(String jsonString, Class<T> clazz) {
         JSONObject jsonObject = JSONObject.fromObject(jsonString);
         T bean = (T) JSONObject.toBean(jsonObject, clazz);
         return bean;
     }

     /**
      * 从json HASH表达式中获取一个map，改map支持嵌套功能
      *
      * @param jsonString
      * @return
      */
     @SuppressWarnings({ "unchecked" })
     public static<E, V> Map<E, V> jsonString2Map(String jsonString) {
         JSONObject jsonObject = JSONObject.fromObject(jsonString);
         Iterator<E> keyIter = jsonObject.keys();
         E key;
         V value;
         Map<E, V> valueMap = new HashMap<E, V>();
         while (keyIter.hasNext()) {
             key = (E)keyIter.next();
             value = (V)jsonObject.get(key);
             valueMap.put(key, value);
         }
         return valueMap;
     }

     /**
      * 从json对象集合表达式中得到一个java对象列表
      *
      * @param jsonString
      * @param beanClass
      * @return
      */
     @SuppressWarnings("unchecked")
     public static <T> List<T> json2ObjectList(String jsonString, Class<T> beanClass) {
         JSONArray jsonArray = JSONArray.fromObject(jsonString);
         JSONObject jsonObject;
         T bean;
         int size = jsonArray.size();
         List<T> list = new ArrayList<T>(size);
         for (int i = 0; i < size; i++) {
             jsonObject = jsonArray.getJSONObject(i);
             bean = (T) JSONObject.toBean(jsonObject, beanClass);
             list.add(bean);
         }
         return list;
     }

     /**
      * 从json数组中得到相应java数组
      *
      * @param jsonString
      * @return
      */
     public static Object[] jsonToObjectArray(String jsonString) {
         JSONArray jsonArray = JSONArray.fromObject(jsonString);
         return jsonArray.toArray();
     }

     /**
      * 从json数组中解析出java字符串数组
      *
      * @param jsonString
      * @return
      */
     public static String[] jsonToStringArray(String jsonString) {
         JSONArray jsonArray = JSONArray.fromObject(jsonString);
         String[] stringArray = new String[jsonArray.size()];
         int size = jsonArray.size();
         for (int i = 0; i < size; i++) {
             stringArray[i] = jsonArray.getString(i);
         }
         return stringArray;
     }

     /**
      * 从json数组中解析出javaLong型对象数组
      *
      * @param jsonString
      * @return
      */
     public static Long[] jsonToLongArray(String jsonString) {
         JSONArray jsonArray = JSONArray.fromObject(jsonString);
         int size = jsonArray.size();
         Long[] longArray = new Long[size];
         for (int i = 0; i < size; i++) {
             longArray[i] = jsonArray.getLong(i);
         }
         return longArray;
     }

     /**
      * 从json数组中解析出java Integer型对象数组
      *
      * @param jsonString
      * @return
      */
     public static Integer[] jsonToIntegerArray(String jsonString) {
         JSONArray jsonArray = JSONArray.fromObject(jsonString);
         int size = jsonArray.size();
         Integer[] integerArray = new Integer[size];
         for (int i = 0; i < size; i++) {
             integerArray[i] = jsonArray.getInt(i);
         }
         return integerArray;
     }

     /**
      * 从json数组中解析出java Double型对象数组
      *
      * @param jsonString
      * @return
      */
     public static Double[] jsonToDoubleArray(String jsonString) {
         JSONArray jsonArray = JSONArray.fromObject(jsonString);
         int size = jsonArray.size();
         Double[] doubleArray = new Double[size];
         for (int i = 0; i < size; i++) {
             doubleArray[i] = jsonArray.getDouble(i);
         }
         return doubleArray;
     }

     public static void main(String[] args) {
         User user = new User();
         user.setUsername("admin");
         user.setPassword("123");
         user.setAge(20);
         User user2 = new User();
         user2.setUsername("admin2");
         user2.setPassword("123456");
         user2.setAge(24);
         System.out.println("一：" + JsonUtil.obj2JsonString(user));

         Map<String, String> map11 = new HashMap<String, String>();
         map11.put("1", "a");
         map11.put("2", "b");
         System.out.println("二：" + JsonUtil.obj2JsonString(map11));

         System.out.println("****************************************************************");
         List<User> list = new ArrayList<User>();
         list.add(user);
         list.add(user2);
         System.out.println("三：" + JsonUtil.list2JsonString(list));
         System.out.println("四：" + JsonUtil.list2JsonString_(list));

         System.out.println("****************************************************************");
         // 只包含数组里面的属性
         System.out.println("五：" + JsonUtil.obj2JsonString(user, new String[] { "username" }, true));
         // 除数组之外的所有属性
         System.out.println("六：" + JsonUtil.obj2JsonString(user, new String[] { "username" }, false));

         System.out.println("七：" + JsonUtil.list2JsonString(list, new String[] { "username", "password" }, true));

         System.out.println("****************************************************************");
         Map<String, User> map1 = new HashMap<String, User>();
         map1.put("1", user);
         map1.put("2", user2);
         System.out.println("八：" + JsonUtil.map2JsonString(map1, new String[] { "username", "password" }, true));

         Map<String, List<User>> map2 = new HashMap<String, List<User>>();
         map2.put("1", list);
         System.out.println("九：" + JsonUtil.map2JsonString(map2, new String[] { "username", "password" }, true));

     }

 }

打印结果：

一：{"username":"admin","age":20,"password":"123"}
二：{"2":"b","1":"a"}
****************************************************************
三：[{"username":"admin","age":20,"password":"123"},{"username":"admin2","age":24,"password":"123456"}]
四：[
{"username":"admin","age":20,"password":"123"},
{"username":"admin2","age":24,"password":"123456"}
]
****************************************************************
五：{"username":"admin","age":20,"password":"123"}
六：{"age":20,"password":"123"}
七：[{"username":"admin","age":20,"password":"123"},{"username":"admin2","age":24,"password":"123456"}]
****************************************************************
八：{"2":{"username":"admin2","age":24,"password":"123456"},"1":{"username":"admin","age":20,"password":"123"}}
九：{"1":[{"username":"admin","age":20,"password":"123"},{"username":"admin2","age":24,"password":"123456"}]}
****************************************************************
十：[{"username":"admin","age":20,"password":"123"},{"username":"admin2","age":24,"password":"123456"}]
十一：{"2":{"username":"admin2","age":24,"password":"123456"},"1":{"username":"admin","age":20,"password":"123"}}
十二：{"1":[{"username":"admin","age":20,"password":"123"},{"username":"admin2","age":24,"password":"123456"}]}