首先建立两个实体类，Student.java 和 Teacher.java
public class Student { ???????????private int id; ?????private String name; ?????private int age; ???????????/** ?????* 默认的构造方法必须不能省，不然不能解析 ?????*/ ???????????public Student(){ ???????????????} ?????public Student(int id,String name,int age) { ?????????this.id = id; ?????????this.name = name; ?????????this.age = age; ?????} ???????public int getId() { ?????????return id; ?????} ???????public void setId(int id) { ?????????this.id = id; ?????} ???????public String getName() { ?????????return name; ?????} ???????public void setName(String name) { ?????????this.name = name; ?????} ???????public int getAge() { ?????????return age; ?????} ???????public void setAge(int age) { ?????????this.age = age; ?????} ???????????@Override ?????public String toString() { ?????????return "Student [id=" + id + ", name=" + name + ", age=" + age + "]"; ?????} ???????} ?public class Teacher { ???????????private int id; ?????private String name; ???????????private List<Student> students; ?????????????/** ?????* 默认的构造方法必须不能省，不然不能解析 ?????*/ ?????public Teacher() { ???????????????} ?????public Teacher(int id,String name) { ?????????this.id = id; ?????????this.name = name; ?????} ???????????public int getId() { ?????????return id; ?????} ?????public void setId(int id) { ?????????this.id = id; ?????} ?????public String getName() { ?????????return name; ?????} ?????public void setName(String name) { ?????????this.name = name; ?????} ???????public List<Student> getStudents() { ?????????return students; ?????} ?????public void setStudents(List<Student> students) { ?????????this.students = students; ?????} ?????@Override ?????public String toString() { ?????????return "Teacher [id=" + id + ", name=" + name + ", mStudents=" ?????????????????+ students + "]"; ?????} ?????????????} ?对象转为json串
public class App { ???public static void main(String[] args) { ???????Student student = new Student(0, "Aaron", 24); ???????System.out.println(JSON.toJSONString(student)); ???????List<Student> students = new ArrayList<Student>(); ???????for(int i=0;i<5;i++) { ???????????Student stu = new Student(i, "Student" + i, 18 +i); ???????????students.add(stu); ???????} ???????System.out.println(JSON.toJSONString(students)); ???????List<Teacher> teaList = new ArrayList<Teacher>(); ???????long time = System.currentTimeMillis(); ???????for(int i=0;i<10;i++) { ???????????Teacher teacher = new Teacher(i, "Teacher " + i); ???????????List<Student> stus = new ArrayList<Student>(); ???????????for(int j = 0 ;j<4;j++) { ???????????????Student s = new Student(j, "Student" + j, 18 +j); ???????????????stus.add(s); ???????????} ???????????teacher.setStudents(stus); ???????????teaList.add(teacher); ???????} ???????String jsonTeach = JSON.toJSONString(teaList); ???????System.out.println("fastjson = " + jsonTeach); ???????System.out.println("=========================================="); ???????Student student1 = new Student(0, "Aaron", 24); ???????System.out.println(JSON.toJSONString(student1,true)); ???}}json串转为对象
public class TestParseToObject { ???public static void main(String[] args) { ???????Student student = new Student(0, "Aaron", 24); ???????String str = JSON.toJSONString(student,true); ???????System.out.println(JSON.parseObject(str,Student.class)); ???????System.out.println("================================================="); ???????List<Student> students = new ArrayList<Student>(); ???????for(int i=0;i<5;i++) { ???????????Student stu = new Student(i, "Student" + i, 18 +i); ???????????students.add(stu); ???????} ???????// 过滤哪些属性需要转换// ?????SimplePropertyPreFilter filter = new SimplePropertyPreFilter(Student.class, "id","age");// ?????String jsonStu =JSON.toJSONString(students,filter); ???????String jsonStu = JSON.toJSONString(students); ???????System.out.println(jsonStu);// ???????List<Student> stu =JSON.parseObject(jsonStu, new TypeReference<List<Student>>(){}); ???????List<Student> stu =JSON.parseArray(jsonStu, Student.class); ???????for(int i=0;i<stu.size();i++) ???????{ ???????????System.out.println(stu.get(i)); ???????} ???}}日期相关
1.日期格式化：
FastJSON可以直接对日期类型格式化，在缺省的情况下，FastJSON会将Date转成long。
例5：FastJSON将java.util.Date转成long。
1 String dateJson = JSON.toJSONString(new Date());2 ????????3 System.out.println(dateJson);
输出结果：
1401370199040
例6：使用SerializerFeature特性格式化日期。
1 String dateJson = JSON.toJSONString(new Date(), SerializerFeature.WriteDateUseDateFormat);2 ????????3 System.out.println(dateJson);
输出结果：
"2014-05-29 21:36:24"
也可以指定输出日期格式。
例7：指定输出日期格式。
1 String dateJson = JSON.toJSONStringWithDateFormat(new Date(), "yyyy-MM-dd HH:mm:ss.SSS");2 ????????3 System.out.println(dateJson);
输出结果：
"2014-05-29 21:47:00.154"
2.使用单引号。
例8：以例2为例。
String listJson = JSON.toJSONString(list, SerializerFeature.UseSingleQuotes);
输出结果：
[{‘key1‘:‘One‘,‘key2‘:‘Two‘},{‘key3‘:‘Three‘,‘key4‘:‘Four‘}]3.JSON格式化。
例9：
String listJson = JSON.toJSONString(list, SerializerFeature.PrettyFormat);
输出结果：与例4结果一致。
4.输出Null字段。
缺省情况下FastJSON不输入为值Null的字段，可以使用SerializerFeature.WriteMapNullValue使其输出。
例10：
1 Map<String, Object> map = new HashMap<String,Object>();2 ????????3 String b = null;4 Integer i = 1;5 ????????6 map.put("a", b);7 map.put("b", i);8 ????????9 String listJson = JSON.toJSONString(map, SerializerFeature.WriteMapNullValue);输出结果：
{"a":null,"b":1}JSONObject，JSONArray是JSON的两个子类
JSONObject相当于Map<String, Object>，
JSONArray相当于List<Object>。
简单方法示例：
例16：将Map转成JSONObject，然后添加元素，输出。
1 Map<String, Object> map = new HashMap<String, Object>(); 2 map.put("key1", "One"); 3 map.put("key2", "Two"); 4 ????????????????????????????5 JSONObject j = new JSONObject(map); 6 ????????????????????7 j.put("key3", "Three"); 8 ???????????9 System.out.println(j.get("key1"));10 System.out.println(j.get("key2"));11 System.out.println(j.get("key3"));输出结果：
1 One2 Two3 Three
例17：将List对象转成JSONArray，然后输出。
1 List<Map<String, Object>> list = new ArrayList<Map<String, Object>>(); 2 ?????????3 Map<String, Object> map = new HashMap<String, Object>(); 4 map.put("key1", "One"); 5 map.put("key2", "Two"); 6 ?????????7 Map<String, Object> map2 = new HashMap<String, Object>(); 8 map2.put("key1", "Three"); 9 map2.put("key2", "Four");10 ????????11 list.add(map);12 list.add(map2);13 ????????14 JSONArray j = JSONArray.parseArray(JSON.toJSONString(list));15 ?????????16 for(int i=0; i<j.size(); i++){17 ????System.out.println(j.get(i));18 }输出结果：
1 {"key1":"One","key2":"Two"}2 {"key1":"Three","key2":"Four"}FastJson简单使用
原文地址：https://www.cnblogs.com/zailushang1996/p/8480675.html