注意来自不同3个jar包的JSONObject的区别

com.alibaba.fastjson.JSONObjectnet.sf.json.JSONObjectorg.json.JSONObject

java对象和json数据之间的转换方式一般有两种，一种是引用第三方的jar包，如Gson（谷歌）、Fastjson（阿里）、Jackson等，这种方式优点是语法精练，可以实现一句话转化，但缺点是会引入庞大的第三方库，第二种是直接使用Java自带的org.json解析，但这个库功能比较基础，解析会写很多重复的代码

一 、com.alibaba.fastjson.JSONObject的使用

1 POM.xml

<!-- https://mvnrepository.com/artifact/com.alibaba/fastjson --> <dependency> <groupId>com.alibaba</groupId> <artifactId>fastjson</artifactId> <version>1.2.51</version> </dependency>

2 附上代码例子

2.1 创建2个实体类，供后面例子使用

public class School { private String id; private String name; List<User> students = new ArrayList<User>(); public String getId() { return id; } public void setId(String id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public List<User> getStudents() { return students; } public void setStudents(List<User> students) { this.students = students; } } public class User { private String id; private String name; public User(){ } public User(String id, String name){ this.id = id; this.name = name; } public String getId() { return id; } public void setId(String id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } }

2.2 Json字符串与Map、List、object之间的相互转换

import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import com.alibaba.fastjson.JSON; import com.alibaba.fastjson.JSONArray; import com.alibaba.fastjson.JSONObject; public class TestFastJson { public static void main(String[] args){ json2JsonObject();//将Json字符串转换为JSONObject对象 json2JavaBean();//将Json字符串转换为JavaBean对象 json2JsonArray();//将Json字符串转换为JSONArray对象 json2JavaBeanList();//将Json字符串转换为JavaBean的集合 javaBean2Json();//将JavaBean转换为Json格式的数据 javaBean2JsonObject();//将JavaBean转换为JSONObject对象 json2ListInMap();//从Json字符串的Map中获取List对象 list2JsonInMap();//将含list的Map对象转换为Json字符串 stringToMap();//json字符串转map mapToString();//map转json字符串 mapToJsonObject();//map转json对象 testList2String()；//list转json字符串 } private static void json2JsonObject() { String s = "{\"name\":\"peter\"}"; JSONObject object = JSON.parseObject(s); System.out.println(object.get("name")); } private static void json2JavaBean() { String s = "{\"id\":\"17051801\",\"name\":\"lucy\"}"; User user = JSON.parseObject(s, User.class); System.out.println(user.getId()); System.out.println(user.getName()); } private static void json2JsonArray() { String s = "[{\"id\":\"17051801\",\"name\":\"lucy\"},{\"id\":\"17051802\",\"name\":\"peter\"}]"; JSONArray array = JSON.parseArray(s); for (int i = 0; i < array.size(); i++) { //JSONArray中的数据转换为String类型需要在外边加"";不然会报出类型强转异常！ String str = array.get(i)+""; JSONObject object = JSON.parseObject(str); System.out.println(object.get("name")); } } private static void json2JavaBeanList() { String s = "[{\"id\":\"17051801\",\"name\":\"lucy\"},{\"id\":\"17051802\",\"name\":\"peter\"}]"; List<User> list = JSON.parseArray(s, User.class); for (User user : list) { System.out.println(user.getName()); } } private static void javaBean2Json() { User user = new User("17051801", "lucy"); String string = JSON.toJSONString(user); System.out.println(string); } private static void javaBean2JsonObject() { User user = new User("17051801", "lucy"); JSONObject json = (JSONObject) JSON.toJSON(user); System.out.println(json.get("id")); } private static void json2ListInMap() { String s = "{json:[{id:\"17051801\",\"name\":\"lucy\"},{id:\"17051802\",\"name\":\"peter\"}," + "{id:\"17051803\",\"name\":\"tom\"},{id:\"17051804\",\"name\":\"lily\"}]}"; //将Json字符串转换为JSONObject对象,并取出list对象的值 JSONObject object = JSON.parseObject(s); Object objArray = object.get("json"); String str = objArray+""; //方式1:转换成JSONArray对象形式 JSONArray array = JSON.parseArray(str); for (int i = 0; i < array.size(); i++) { JSONObject obj = JSON.parseObject(array.get(i)+""); System.out.println(obj.get("name")); } //方式2:转换成List<JavaBean>形式 List<User> list = JSON.parseArray(str, User.class); for (User user : list) { System.out.println(user.getName()); } } private static void list2JsonInMap() { //方式1:构建一个带有list的JavaBean对象 School school = new School(); school.setId("1"); school.setName("schoolA"); User user1 = new User(); user1.setId("17051801"); user1.setName("lucy"); User user2 = new User(); user2.setId("17051802"); user2.setName("peter"); school.getStudents().add(user1); school.getStudents().add(user2); //将JavaBean对象转换成Json字符串 String string1 = JSON.toJSONString(school); System.out.println(string1); //方式2:构建一个带有list的Map对象 Map<String, Object> map1 = new HashMap<String,Object>(); map1.put("id", "17051801"); map1.put("name", "lucy"); Map<String, Object> map2 = new HashMap<String,Object>(); map2.put("id", "17051802"); map2.put("name", "peter"); List<Map<String, Object>> list = new ArrayList<Map<String, Object>>(); list.add(map1); list.add(map2); Map<String, Object> map = new HashMap<String,Object>(); map.put("id", "1"); map.put("name", "schoolA"); map.put("students", list); //将map对象转换成Json字符串 String string2 = JSON.toJSONString(map); System.out.println(string2); } private static void stringToMap(){ String str = "{\"age\":\"24\",\"name\":\"cool_summer_moon\"}"; JSONObject jsonObject = JSONObject.parseObject(str); //json对象转Map Map<String,Object> map = (Map<String,Object>)jsonObject; System.out.println("map对象是：" + map); Object object = map.get("age"); System.out.println("age的值是"+object); } private static void mapToString(){ Map<String,Object> map = new HashMap<>(); map.put("age", 24); map.put("name", "cool_summer_moon"); String jsonString = JSON.toJSONString(map); System.out.println("json字符串是："+jsonString); } private static void mapToJsonObject(){ Map<String,Object> map = new HashMap<>(); map.put("age", 24); map.put("name", "cool_summer_moon"); JSONObject json = new JSONObject(map); System.out.println("Json对象是：" + json); } /** * 测试包装类型的List转换为json字符串 */ public static void testList2String() { List<Long> longs = new ArrayList<Long>(); longs.add(1L); longs.add(2L); longs.add(3L); String actual = JSON.toJSONString(longs); Assert.assertEquals("[1,2,3]", actual); } }

二 、org.json.JSONObject的使用

1.引入org.json依赖

<!-- 引入org.json所需依赖 --> <dependency> <groupId>org.json</groupId> <artifactId>json</artifactId> <version>20160810</version> </dependency>

2 构建JSONObject (3种)

2.1 直接构建

可以直接使用 new 关键字实例化一个JSONObject对象，然后调用它的 put() 方法对其字段值进行设置。

范例 JSONObject jsonObj = new JSONObject(); jsonObj.put("female", true); jsonObj.put("hobbies", Arrays.asList(new String[] { "yoga", "swimming" })); jsonObj.put("discount", 9.5); jsonObj.put("age", "26"); jsonObj.put("features", new HashMap<String, Integer>() { private static final long serialVersionUID = 1L; { put("height", 175); put("weight", 70); } }); System.out.println(jsonObj); 结果 { "features": { "weight": 70, "height": 175 }, "hobbies": ["yoga", "swimming"], "discount": 9.5, "female": true, "age": 26 }

2.2 使用Map构建

范例 Map<String, Object> map = new HashMap<String, Object>(); map.put("female", true); map.put("hobbies", Arrays.asList(new String[] { "yoga", "swimming" })); map.put("discount", 9.5); map.put("age", "26"); map.put("features", new HashMap<String, Integer>() { private static final long serialVersionUID = 1L; { put("height", 175); put("weight", 70); } }); JSONObject jsonObj = new JSONObject(map); System.out.println(jsonObj); 结果 { "features": { "weight": 70, "height": 175 }, "hobbies": ["yoga", "swimming"], "discount": 9.5, "female": true, "age": 26 }

2.3 使用JavaBean构建

范例 import java.util.Map; public class UserInfo { private Boolean female; private String[] hobbies; private Double discount; private Integer age; private Map<String, Integer> features; public Boolean getFemale() { return female; } public void setFemale(Boolean female) { this.female = female; } public String[] getHobbies() { return hobbies; } public void setHobbies(String[] hobbies) { this.hobbies = hobbies; } public Double getDiscount() { return discount; } public void setDiscount(Double discount) { this.discount = discount; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } public Map<String, Integer> getFeatures() { return features; } public void setFeatures(Map<String, Integer> features) { this.features = features; } } UserInfo userInfo = new UserInfo(); userInfo.setFemale(true); userInfo.setHobbies(new String[] { "yoga", "swimming" }); userInfo.setDiscount(9.5); userInfo.setAge(26); userInfo.setFeatures(new HashMap<String, Integer>() { private static final long serialVersionUID = 1L; { put("height", 175); put("weight", 70); } }); JSONObject jsonObj = new JSONObject(userInfo); System.out.println(jsonObj); 结果 { "features": { "weight": 70, "height": 175 }, "hobbies": ["yoga", "swimming"], "discount": 9.5, "female": true, "age": 26 }

3.解析JSONObject

JSONObject为每一种数据类型都提供了一个getXXX(key)方法，例如：获取字符串类型的字段值就使用getString()方法，获取数组类型的字段值就使用getJSONArray()方法。

范例 // 获取基本类型数据 System.out.println("Female: " + jsonObj.getBoolean("female")); System.out.println("Discount: " + jsonObj.getDouble("discount")); System.out.println("Age: " + jsonObj.getLong("age")); // 获取JSONObject类型数据 JSONObject features = jsonObj.getJSONObject("features"); String[] names = JSONObject.getNames(features); System.out.println("Features: "); for (int i = 0; i < names.length; i++) { System.out.println("\t"+features.get(names[i])); } // 获取数组类型数据 JSONArray hobbies = jsonObj.getJSONArray("hobbies"); System.out.println("Hobbies: "); for (int i = 0; i < hobbies.length(); i++) { System.out.println("\t"+hobbies.get(i)); } 结果 Female: true Discount: 9.5 Age: 26 Features: 70 175 Hobbies: yoga swimming

三 net.sf.json.JSONObject的使用

1 引入maven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>

使用范例

JSONObject_1_3 package json; import net.sf.json.JSON; import net.sf.json.JSONObject; import net.sf.json.xml.XMLSerializer; public class JSONObject_1_3 { public static void javaToJSON() { System.out.println("java代码封装为json字符串"); JSONObject jsonObj = new JSONObject(); jsonObj.put("username", "张三"); jsonObj.put("password", "123456"); System.out.println("java--->json \n" + jsonObj.toString()); } public static void jsonToJAVA() { System.out.println("json字符串转java代码"); String jsonStr = "{\"password\":\"123456\",\"username\":\"张三\"}"; JSONObject jsonObj = JSONObject.fromString(jsonStr); String username = jsonObj.getString("username"); String password = jsonObj.optString("password"); System.out.println("json--->java\n username=" + username + "\t password=" + password); } public static void jsonToXML() { System.out.println("json字符串转xml字符串"); String jsonStr = "{\"password\":\"123456\",\"username\":\"张三\"}"; JSONObject json = JSONObject.fromString(jsonStr); XMLSerializer xmlSerializer = new XMLSerializer(); xmlSerializer.setRootName("user_info"); xmlSerializer.setTypeHintsEnabled(false); String xml = xmlSerializer.write(json); System.out.println("json--->xml \n" + xml); } public static void javaBeanToJSON() { System.out.println("javabean转json字符串"); UserInfo userInfo = new UserInfo(); userInfo.setUsername("张三"); userInfo.setPassword("123456"); JSONObject json = JSONObject.fromBean(userInfo); System.out.println("javabean--->json \n" + json.toString()); } public static void javaBeanToXML() { System.out.println("javabean转xml字符串"); UserInfo userInfo = new UserInfo(); userInfo.setUsername("张三"); userInfo.setPassword("123456"); JSONObject json = JSONObject.fromBean(userInfo); XMLSerializer xmlSerializer = new XMLSerializer(); String xml = xmlSerializer.write(json, "UTF-8"); System.out.println("javabean--->xml \n" + xml); } public static void xmlToJSON(){ System.out.println("xml字符串转json字符串"); String xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?><user_info><password>123456</password><username>张三</username></user_info>"; JSON json=XMLSerializer.read(xml); System.out.println("xml--->json \n"+json.toString()); } public static void main(String args[]) { // javaToJSON(); // jsonToJAVA(); // jsonToXML(); // javaBeanToJSON(); // javaBeanToXML(); xmlToJSON(); } } UserInfo package json; public class UserInfo { public String username; public 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; } }