jsonobject判断key是否存在某个key_java的foreach用法

jsonobject判断key是否存在某个key_java的foreach用法 在程序开发过程中，在参数传递，函数返回值等方面，越来越多的使用JSON。

JSON(JavaScript Object Notation)是一种轻量级的数据交换格式，同时也易于机器解析和生成、易于理解、阅读和撰写，而且Json采用完全独立于语言的文本格式，这使得Json成为理想的数据交换语言。

JSON建构于两种结构：“名称/值”对的集合(A Collection of name/value pairs)，在不同的语言中，它被理解为对象(Object), 记录(record), 结构(struct), 字典(dictionary), 有趣列表(keyed list), 哈希表(hash table)或者关联数组(associative array)。

JSONObject依赖：最后一行需要保留，有两个jdk版本的实现：json-lib-2.1-jdk13.jar和json-lib-2.1-jdk15.jar<dependency> <groupId>net.sf.json-lib</groupId> <artifactId>json-lib</artifactId> <version>2.4</version> <classifier>jdk15</classifier></dependency>使用net.sf.json需要导入的jar包jar包下载：https://pan.baidu.com/s/1iZiXw55TPwIxYFQQCaR9GwJSONObject创建JSONObject，添加属性//创建JSONObjectJSONObject json = new JSONObject();//添加属性json.put("username", "张三");json.put("password", "123");//打印System.out.println(json); //增加属性json.element("sex", "男");json.put("age", 18);System.out.println(json);根据key返回输出System.out.println(json.get("sex"));判断输出对象的类型boolean isArray = json.isArray();boolean isEmpty = json.isEmpty();boolean isNullObject = json.isNullObject();System.out.println("是否数组："+isArray+", 是否空："+isEmpty+", 是否空为空对象："+isNullObject);把JSONArray添加到JSONObject中/把JSONArray添加到JSONObject中JSONArray jsonArray = new JSONArray();jsonArray.add(0, "张三");jsonArray.add(1, "123");//开始添加json.element("student", jsonArray);System.out.println(json);全部代码：import net.sf.json.JSONArray;import net.sf.json.JSONObject; public class Json {public static void main(String[] args) {//创建JSONObjectJSONObject json = new JSONObject();//添加属性json.put("username", "张三");json.put("password", "123");//打印System.out.println(json);//增加属性json.element("sex", "男");json.put("age", 18);System.out.println(json);//根据key返回System.out.println(json.get("sex"));//判断输出对象的类型boolean isArray = json.isArray();boolean isEmpty = json.isEmpty();boolean isNullObject = json.isNullObject();System.out.println("是否数组："+isArray+", 是否空："+isEmpty+", 是否空为空对象："+isNullObject);System.out.println("=====");//把JSONArray添加到JSONObject中JSONArray jsonArray = new JSONArray();jsonArray.add(0, "张三");jsonArray.add(1, "123");//开始添加json.element("student", jsonArray);System.out.println(json);}}运行结果：JSONArray创建JSONArray，添加属性值//创建JSONArrayJSONArray jsonArray = new JSONArray();//添加jsonArray.add(0, "张三");jsonArray.add(1, "123");jsonArray.element("男");System.根据下标返回输出System.out.println(jsonArray.get(0));根据下标设置新值，修改jsonArray.set(0, "李四");System.out.println(jsonArray);把JSONObject放入到JSONArray中//把JSONObject放入到JSONArray中JSONObject jsonObject = new JSONObject();jsonObject.put("username", "张三");jsonObject.put("password", "123");jsonArray.add(jsonObject);System.全部代码：import net.sf.json.JSONArray;import net.sf.json.JSONObject; public class Json {public static void main(String[] args) {//创建JSONArrayJSONArray jsonArray = new JSONArray();//添加jsonArray.add(0, "张三");jsonArray.add(1, "123");jsonArray.element("男");System.out.println(jsonArray);//根据下标返回输出System.out.println(jsonArray.get(0));//根据下标设置新值，修改jsonArray.set(0, "李四");System.out.println(jsonArray);//把JSONObject放入到JSONArray中JSONObject jsonObject = new JSONObject();jsonObject.put("username", "张三");jsonObject.put("password", "123");jsonArray.add(jsonObject);System.out.println(jsonArray);//循环输出for(int i = 0; i < jsonArray.size(); i++) {System.out.println(jsonArray.get(i));}}}运行结果JavaBean与json字符串互转student类：public class Student {private String username;private String password;public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public String getPassword() {return password;}public void setPassword(String password) {this.password = password;}public Student(String username, String password) {super();this.username = username;this.password = password;}public Student() {super();// TODO Auto-generated constructor stub}@Overridepublic String toString() {return "Student [username=" + username + ", password=" + password + "]";}}定义对象，JavaBean对象转json字符串//定义对象Student stu = new Student("张三", "123456");//JavaBean对象转json字符串JSONObject jsonObject = JSONObject.fromObject(stu);System.out.println(jsonObject);json字符串转为javaBean//json字符串转为javaBean//定义json字符串String jsondata = "{"username":"李四", "password":"123"}";//转为json对象JSONObject json = JSONObject.fromObject(jsondata);//转为JavaBean对象Student stu2 = (Student)JSONObject.toBean(json, Student.class);System.out.println(stu2.toString());全部代码：import net.sf.json.JSONObject; public class Json {public static void main(String[] args) {//定义对象Student stu = new Student("张三", "123456");//JavaBean对象转json字符串JSONObject jsonObject = JSONObject.fromObject(stu);System.out.println(jsonObject);//json字符串转为javaBean//定义json字符串String jsondata = "{"username":"李四", "password":"123"}";//转为json对象JSONObject json = JSONObject.fromObject(jsondata);//转为JavaBean对象Student stu2 = (Student)JSONObject.toBean(json, Student.class);System.out.println(stu2.toString());}}输出结果：List与json字符串互转先定义list集合，list转json字符串//定义list集合List list = new ArrayList();list.add(new Student("张三", "123"));list.add(new Student("李四", "456"));//list转json字符串JSONArray jsonArray = JSONArray.fromObject(list);System.out.println(jsonArray);json字符串转list//json字符串转listList list2 = new ArrayList();String jsondata = "[{"password":"123","username":"张三"},{"password":"456","username":"李四"}]";JSONArray jsonArray1 = JSONArray.fromObject(jsondata);for(int i = 0; i < jsonArray1.size(); i++) {JSONObject jsonObject2 = jsonArray1.getJSONObject(i);Student stu2 = (Student)JSONObject.toBean(jsonObject2, Student.class);list2.add(stu2);}System.out.println(list2);全部代码import java.util.ArrayList;import java.util.List; import net.sf.json.JSONArray;import net.sf.json.JSONObject; public class Json {public static void main(String[] args) {//定义list集合List list = new ArrayList();list.add(new Student("张三", "123"));list.add(new Student("李四", "456"));//list转json字符串JSONArray jsonArray = JSONArray.fromObject(list);System.out.println(jsonArray);//json字符串转listList list2 = new ArrayList();String jsondata = "[{"password":"123","username":"张三"},{"password":"456","username":"李四"}]";JSONArray jsonArray1 = JSONArray.fromObject(jsondata);for(int i = 0; i < jsonArray1.size(); i++) {JSONObject jsonObject2 = jsonArray1.getJSONObject(i);Student stu2 = (Student)JSONObject.toBean(jsonObject2, Student.class);list2.add(stu2);}System.out.println(list2);}}运行结果Map与json字符串互转定义map集合，Map转json字符串//定义map集合Map map = new HashMap();map.put("1", new Student("张三", "123"));map.put("2", new Student("李四", "456"));//Map转json字符串JSONObject jsonMap = JSONObject.fromObject(map);System.out.println(jsonMap);定义字符串map集合，map集合字符串转为map//定义字符串map集合String jsondata = "{"1":{"password":"123","username":"张三"},"2":{"password":"456","username":"李四"}}";//map集合字符串转为mapMap map2 = (Map)JSONObject.fromObject(jsondata);Set set = map2.keySet();//定义迭代器，迭代输出Iterator ite = set.iterator();while(ite.hasNext()) {//取出一个字符串对象String key = (String)ite.next();//转为json格式JSONObject jsonObject = JSONObject.fromObject(map2.get(key));//转为对象Student stu = (Student)JSONObject.toBean(jsonObject, Student.class);System.out.println(key+" "+stu);}全部代码import java.util.HashMap;import java.util.Iterator;import java.util.Map;import java.util.Set; import net.sf.json.JSONObject; public class Json {public static void main(String[] args) {//定义map集合Map map = new HashMap();map.put("1", new Student("张三", "123"));map.put("2", new Student("李四", "456"));//Map转json字符串JSONObject jsonMap = JSONObject.fromObject(map);System.out.println(jsonMap);//定义字符串map集合String jsondata = "{"1":{"password":"123","username":"张三"},"2":{"password":"456","username":"李四"}}";//map集合字符串转为mapMap map2 = (Map)JSONObject.fromObject(jsondata);Set set = map2.keySet();//定义迭代器，迭代输出Iterator ite = set.iterator();while(ite.hasNext()) {//取出一个字符串对象String key = (String)ite.next();//转为json格式JSONObject jsonObject = JSONObject.fromObject(map2.get(key));//转为对象Student stu = (Student)JSONObject.toBean(jsonObject, Student.class);System.out.println(key+" "+stu);}}}运行结果:SONArray与List互转定义list集合，List转型JSONArray//定义list集合List<Student> list = new ArrayList<Student>();list.add(new Student("张三", "123"));list.add(new Student("李四", "456"));//List转型JSONArrayJSONArray jsonArray = JSONArray.fromObject(list);System.out.println(jsonArray.toString());JSONArray转型List，JSONArray是用的上面的那个jsonArray变量//JSONArray转型ListList<Student> list2 = JSONArray.toList(jsonArray, new Student(), new JsonConfig());Iterator<Student> ite = list2.iterator();while(ite.hasNext()) {Student stu = ite.next();System.out.println(stu);}全部代码import java.util.ArrayList;import java.util.Iterator;import java.util.List; import net.sf.json.JSONArray;import net.sf.json.JsonConfig; public class Json {public static void main(String[] args) {//定义list集合List<Student> list = new ArrayList<Student>();list.add(new Student("张三", "123"));list.add(new Student("李四", "456"));//List转型JSONArrayJSONArray jsonArray = JSONArray.fromObject(list);System.out.println(jsonArray.toString());//JSONArray转型ListList<Student> list2 = JSONArray.toList(jsonArray, new Student(), new JsonConfig());Iterator<Student> ite = list2.iterator();while(ite.hasNext()) {Student stu = ite.next();System.out.println(stu);}}}运行结果JSONArray与数组互转定义数组，数组转JSONArray//定义数组boolean[] boolArray = {true, false, true};//java数组转JSONArrayJSONArray jsonArray = JSONArray.fromObject(boolArray);System.out.println(jsonArray.toString());JSONArray转java数组//JSONArray转java数组Object obj[] = jsonArray.toArray();for(Object o : obj) {System.out.print(o+"t");}全部代码import net.sf.json.JSONArray; public class Json {public static void main(String[] args) {//定义数组boolean[] boolArray = {true, false, true};//java数组转JSONArrayJSONArray jsonArray = JSONArray.fromObject(boolArray);System.out.println(jsonArray.toString());//JSONArray转java数组Object obj[] = jsonArray.toArray();for(Object o : obj) {System.out.print(o+"t");}}}