Java如何将集合转换为JSON？
本示例说明如何将Java集合对象转换为JSON字符串。对于Student在本示例中使用的类，您可以在前面的示例中找到如何将对象转换为JSON？
package org.nhooo.example.google.gson;
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.List;
public class CollectionToJson {
public static void main(String[] args) {
//将字符串对象的集合转换为JSON字符串。
List<String> names = new ArrayList<String>();
names.add("Alice");
names.add("Bob");
names.add("Carol");
names.add("Mallory");
Gson gson = new Gson();
String jsonNames = gson.toJson(names);
System.out.println("jsonNames = " + jsonNames);
//将集合Student对象转换为JSON字符串
Student a = new Student("Alice", "Apple St", getDOB(2000, 10, 1));
Student b = new Student("Bob", "Banana St", null);
Student c = new Student("Carol", "Grape St", getDOB(2000, 5, 21));
Student d = new Student("Mallory", "Mango St", null);
List<Student> students = new ArrayList<Student>();
students.add(a);
students.add(b);
students.add(c);
students.add(d);
gson = new Gson();
String jsonStudents = gson.toJson(students);
System.out.println("jsonStudents = " + jsonStudents);
//将JSON字符串转换为Student对象的集合。
Type type = new TypeToken<List<Student>>() {}.getType();
List<Student> studentList = gson.fromJson(jsonStudents, type);
for (Student student : studentList) {
System.out.println("student.getName() = " + student.getName());
}
}
private static Date getDOB(int year, int month, int date) {
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.YEAR, year);
calendar.set(Calendar.MONTH, month - 1);
calendar.set(Calendar.DATE, date);
calendar.set(Calendar.HOUR, 0);
calendar.set(Calendar.MINUTE, 0);
calendar.set(Calendar.SECOND, 0);
return calendar.getTime();
}
}这是我们程序的结果：
jsonNames = ["Alice","Bob","Carol","Mallory"]
jsonStudents = [{"name":"Alice","address":"Apple St","dateOfBirth":"Nov 1, 3900 12:00:00 AM"},{"name":"Bob","address":"Banana St"},{"name":"Carol","address":"Grape St","dateOfBirth":"Jun 21, 3900 12:00:00 AM"},{"name":"Mallory","address":"Mango St"}]
student.getName() = Alice
student.getName() = Bob
student.getName() = Carol
student.getName() = MalloryMaven依赖
<!-- http://repo1.maven.org/maven2/com/google/code/gson/gson/2.8.0/gson-2.8.0.jar -->
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.8.0</version>
</dependency>