Jackson数据绑定泛型 - Jackson教程

在简单的数据绑定中，我们使用String作为关键对象，并作为一个值对象映射类。相反，我们可以使用具体的Java对象和类型强制转换到JSON使用。

考虑下面的例子使用一个类的UserData来保存用户专用数据。

创建一个名为JacksonTester在Java类文件目录 C:\>Jackson_WORKSPACE.

文件名: JacksonTester.java

import java.io.File;
import java.io.IOException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.JsonParseException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.type.TypeReference;

public class JacksonTester {
   public static void main(String args[]){
      JacksonTester tester = new JacksonTester();
         try {
            ObjectMapper mapper = new ObjectMapper();

            Map <string, style="box-sizing: border-box;" userdata="">userDataMap = new HashMap<string, style="box-sizing: border-box;" userdata="">();
            UserData studentData = new UserData(); 
            int[] marks = {1,2,3};

            Student student = new Student();
            student.setAge(10);
            student.setName("Mahesh");
            // JAVA Object
            studentData.setStudent(student);
            // JAVA String
            studentData.setName("Mahesh Kumar");
            // JAVA Boolean
            studentData.setVerified(Boolean.FALSE);
            // Array
            studentData.setMarks(marks);
            TypeReference ref = new TypeReference<map<string,userdata style="box-sizing: border-box;">>() { };
            userDataMap.put("studentData1", studentData);
            mapper.writeValue(new File("student.json"), userDataMap);
            //{
            //   "studentData1":
            //     {
            //        "student":
            //        {
            //            "name":"Mahesh",
            //            "age":10
            //      },
            //      "name":"Mahesh Kumar",
            //      "verified":false,
            //      "marks":[1,2,3]
            //   }
            //}
            userDataMap = mapper.readValue(new File("student.json"), ref);

            System.out.println(userDataMap.get("studentData1").getStudent());
            System.out.println(userDataMap.get("studentData1").getName());
            System.out.println(userDataMap.get("studentData1").getVerified());
            System.out.println(Arrays.toString(userDataMap.get("studentData1").getMarks()));
      } catch (JsonParseException e) {
         e.printStackTrace();
      } catch (JsonMappingException e) {
         e.printStackTrace();
      } catch (IOException e) {
            e.printStackTrace();
      }
   }
}

class Student {
   private String name;
   private int age;
   public Student(){}
   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;
   }
   public String toString(){
      return "Student [ name: "+name+", age: "+ age+ " ]";
   }    
}

class UserData {
   private Student student;
   private String name;
   private Boolean verified;
   private int[] marks;

   public UserData(){}

   public Student getStudent() {
      return student;
   }
   public void setStudent(Student student) {
      this.student = student;
   }
   public String getName() {
      return name;
   }
   public void setName(String name) {
      this.name = name;
   }
   public Boolean getVerified() {
      return verified;
   }
   public void setVerified(Boolean verified) {
      this.verified = verified;
   }
   public int[] getMarks() {
      return marks;
   }
   public void setMarks(int[] marks) {
      this.marks = marks;
   }        
}</map<string,userdata></string,></string,>

验证输出

使用javac编译如下类：

C:\Jackson_WORKSPACE>javac JacksonTester.java

现在运行jacksonTester看到的结果：

C:\Jackson_WORKSPACE>java JacksonTester

验证输出

Student [ name: Mahesh, age: 10 ]
Mahesh Kumar
false
[1, 2, 3]