json是一种轻量级数据交换格式，易于人阅读和编写，同时也易于机器解析和生成
json数据格式
json数组
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> <script type="text/javascript"> /** * 定义json的数组格式 *中括号包裹，数组的元素的数据没有限制 * 元素之间逗号隔开 */ var jsonArray = ["k1","k2",100,9.9,true] // 遍历数组，取出数组中的元素 for (var i = 0 ; i < jsonArray.length ; i++){ console.log(jsonArray[i]); } </script> </head> <body> </body> </html>json对象
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> <script type="text/javascript"> /** * 定义json的对象格式 * 大括号包裹，定义赋值对，键必须是字符串类型，值的数据类型不限制 * 键值对之间是冒号分开的 * 每个键值对之间逗号分开 */ var jsonObject = {"k1":"v1","k2":"v2","k3":100,"k4":9.9,"k5":true}; // 取出键值对，键找值的方式 console.log(jsonObject.k1); console.log(jsonObject.k2); console.log(jsonObject.k3); console.log(jsonObject.k4); console.log(jsonObject.k5); </script> </head> <body> </body> </html>json嵌套
数组套对象
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>json数据的嵌套</title> </head> <body> <script type="text/javascript"> /** * json数组的元素是对象 * 数组定义2个元素，每个元素是对象 * 对象是键值对形式 */ var jsonArray = [ {"name":"张三","age":20}, {"name":"里斯","age":22} ]; // 取出重要的数据，李四22 console.log( jsonArray[1].name +" == "+ jsonArray[1].age); // 遍历数组，取出数组中的元素 for(var i=0 ; i< jsonArray.length; i++){ console.log(jsonArray[i].name + " == "+ jsonArray[i].age); } </script> </body> </html>对象套数组
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>json数据嵌套</title> </head> <body> <script type="text/javascript"> /** * json数据是对象，对象只是数组 */ var jsonObject = { "k1": ["北京，“天津","上海"], "k2": ["中国","美国","英国"] }; // 取出上海 console.log( jsonObject.k1[2]) // 分别取出看和可的数组，遍历 for (var i =0; i< jsonObject.k1.length; i++){ console.log(jsonObject.k1[i]); } console.log("===========") for (var i =0; i< jsonObject.k2.length; i++){ console.log(jsonObject.k2[i]); } </script> </body> </html>你中有我，我中有你
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>数据嵌套</title> </head> <body> <script type="text/javascript"> /** * json的数据嵌套，你中有我，我中有你 * json的数据本质上是对象 * 对象的键是字符串 * 数组的元素是对象 */ var json= { // 键是K1值是数组，数组的元素是对象 "k1":[ {"name":"张三","age":20}, {"name":"里斯","age":22} ], "k2":[ {"name":"王五","age":24}, {"name":"赵六","age":26} ] }; // 取出数据李四26 console.log(json.k1[1].name+"==="+json.k1[1].age) // 遍历k2键对应的数组 for(var i=0 ; i< json.k2.length; i++) { console.log(json.k2[i].name + " == " + json.k2[i].age); } </script> </body> </html>fastjson
他可以解析json格式的字符串，支持将Java Bean序列化为json字符串，也可以从json字符串反序列化到javaBean。
package src.FastJson; import lombok.Data; import java.util.Date; @Data public class Student { private Integer id; private String name; private Integer age; private String email; private Date birthday; }序列化
对象转json
@Test // java中的对象，Student对象，序列化为json格式字符串 public void testObjectToJson(){ Student student = new Student(); student.setId(1); student.setName("张三"); student.setAge(20); student.setEmail("zs@www.com"); student.setBirthday(getDate()); // student对象，转到json格式字符串 String jsonString = JSON.toJSONString(student); System.out.println(jsonString); // {"age":20,"birthday":0,"email":"zs@www.com","id":1,"name":"张三"} }List转json
@Test // java中的集合List，序列化为json格式字符串 public void testListToJson() { //集合List，存储Student对象 List<Student> list = new ArrayList<Student>(); Student student1 = new Student(); student1.setId(1); student1.setName("张三"); student1.setAge(20); student1.setEmail("zs@www.com"); student1.setBirthday(getDate()); Student student2 = new Student(); student2.setId(2); student2.setName("张"); student2.setAge(20); student2.setEmail("z@www.com"); student2.setBirthday(getDate()); // Student对象存储到List集合中 list.add(student1); list.add(student2); // List集合序列化为json格式字符串 String jsonString = JSON.toJSONString(list); System.out.println(jsonString); //转后的元素是数组，数组的元素是对象 // [{"age":20,"birthday":0,"email":"zs@www.com","id":1,"name":"张三"}, // {"age":20,"birthday":0,"email":"z@www.com","id":2,"name":"张"}] }Map转json
@Test // java中的集合Map，序列化为json格式字符串 public void testMapToJson() { // 创建Map集合，键为字符串类型，值是Student对象 Map<String,Student> map = new HashMap<String,Student>(); Student student1 = new Student(); student1.setId(1); student1.setName("张三"); student1.setAge(20); student1.setEmail("zs@www.com"); student1.setBirthday(getDate()); Student student2 = new Student(); student2.setId(2); student2.setName("张"); student2.setAge(20); student2.setEmail("z@www.com"); student2.setBirthday(getDate()); // Map集合中存储student对象 map.put("student1", student1); map.put("student2", student2); String jsonString = JSON.toJSONString(map); System.out.println(jsonString); // json格式字符串是对象，对象有两个键,键对应的值是Student对象 // [{"age":20,"birthday":0,"email":"zs@www.com","id":1,"name":"张三"}, // {"age":20,"birthday":0,"email":"z@www.com","id":2,"name":"张"}] }反序列化
json转对象
@Test // json格式字符串，反序列化回到java对象 public void testJsonToObject() { String jsonString = "{\"age\":20,\"birthday\":0,\"email\":\"zs@www.com\",\"id\":1,\"name\":\"张三\"}"; // JSON类的静态方法parseObject // 传递要反序列化的json字符串 Student student = JSON.parseObject(jsonString,Student.class); System.out.println(student); // Student(id=1, name=张三, age=20, email=zs@www.com, birthday=Thu Jan 01 08:00:00 CST 1970) }json转list
@Test public void testJsonToList() { String jsonString = "[{\"age\":20,\"birthday\":0,\"email\":\"zs@www.com\",\"id\":1,\"name\":\"张三\"},{\"age\":20,\"birthday\":0,\"email\":\"z@www.com\",\"id\":2,\"name\":\"张\"}]"; // JSON类的静态方法，parseArray // 传递json格式字符串，传递转换后的集合的泛型class对象 List<Student> list = JSON.parseArray(jsonString,Student.class); for (Student student : list) { System.out.println(student); } // Student(id=1, name=张三, age=20, email=zs@www.com, birthday=Thu Jan 01 08:00:00 CST 1970) // Student(id=2, name=张, age=20, email=z@www.com, birthday=Thu Jan 01 08:00:00 CST 1970) }json转map
@Test // JSON格式字符串反序列化到Map public void testJsonToMap() { String jsonString = "{\"1\":{\"age\":20,\"birthday\":0,\"email\":\"zs@www.com\",\"id\":1,\"name\":\"张三\"},\"2\":{\"age\":20,\"birthday\":0,\"email\":\"z@www.com\",\"id\":2,\"name\":\"张\"}}"; // json类的静态方法,paresObject // 直接进行反序列化2，Map没有泛型,泛型没有是不安全的集合 // 转后的集合，必须有泛型 // 调用parseObject，传递参数，T类型,在T类的泛型，传递 Map map = JSON.parseObject(jsonString,new TypeReference<Map<String,Student>>(){}); for (Object key: map.keySet()){ System.out.println(key+":"+map.get(key)); } // 1:Student(id=1, name=张三, age=20, email=zs@www.com, birthday=Thu Jan 01 08:00:00 CST 1970) // 2:Student(id=2, name=张, age=20, email=z@www.com, birthday=Thu Jan 01 08:00:00 CST 1970) }fastjson枚举
import com.alibaba.fastjson.JSON; import com.alibaba.fastjson.serializer.SerializerFeature; import org.junit.Test; import java.util.Date; /** * SerializerFeature枚举：进行序列化时，可以自己定义特殊需求 * json静态方法 toJSONString() * 方法的参数：第一个是要序列化的对象 * 方法的参数：第二个参数SerializerFeature枚举类型的可变参数 * SerializerFeature枚举的常量，做序列化的个性需求 */ public class TestFastJson2 { @Test // WriteNullNumberAsZero 枚举的常量,序列化为null的字段,序列化为零 public void testWriteNullNumberAsZero(){ Student student = new Student(); student.setId(1); student.setName("张三"); // student.setAge(20); student.setEmail("zs@www.com"); student.setBirthday(getDate()); // 方法的参数上添加枚举类型 // 只适用于数字 String jsonString = JSON.toJSONString(student,SerializerFeature.WriteNullNumberAsZero,SerializerFeature.WriteNullNumberAsZero); System.out.println(jsonString); // {"age":0,"birthday":0,"email":"zs@www.com","id":1,"name":"张三"} } @Test // WriteNullStringAsEmpty枚举的常量，序列化为null的字段，值序列化为“” public void testWriteNullStringAsEmpty(){ Student student = new Student(); student.setId(1); student.setName("张三"); student.setAge(20); // student.setEmail("zs@www.com"); student.setBirthday(getDate()); // 方法的参数上添加枚举类型 String jsonString = JSON.toJSONString(student,SerializerFeature.WriteNullStringAsEmpty); System.out.println(jsonString); // {"age":20,"birthday":0,"email":"","id":1,"name":"张三"} } @Test //writeMapNullValue 枚举中的常量,序列化null值的字段 public void testWriteMapNullValue(){ Student student = new Student(); student.setId(1); student.setName("张三"); student.setAge(20); // student.setEmail("zs@www.com"); student.setBirthday(getDate()); // 方法的参数上添加枚举类型 String jsonString = JSON.toJSONString(student, SerializerFeature.WriteMapNullValue); System.out.println(jsonString); // {"age":20,"birthday":0,"email":null,"id":1,"name":"张三"} } public Date getDate() { Date date = new Date(0); return date; } }json注解
jsonfield注解
用于序列化时进行特性定制
@JSONfield注解属性name，指定序列化后的名字
ordinal，指定序列化后的字段顺序
format，指定序列化后的格式
serialize，指定是否序列化该字段
JSonType注解
注解作用于类上
includes要被序列化的字段
order要被序列化的字段的顺序
serialzeFeatures序列化时的特性定义
