Jackson - 树到 Java 对象

• 

  简述

  在此示例中，我们使用 JsonNode 创建了一个树，并将其写入 json 文件并回读树，然后将其转换为学生对象。

  在 C：\>Jackson_WORKSPACE 中创建一个名为“JacksonTester”的 Java 类文件。

  文件： JacksonTester.java

  import java.io.File;
  import java.io.IOException;
  import java.util.Iterator;
  import com.fasterxml.jackson.core.JsonParseException;
  import com.fasterxml.jackson.databind.JsonMappingException;
  import com.fasterxml.jackson.databind.JsonNode;
  import com.fasterxml.jackson.databind.ObjectMapper;
  import com.fasterxml.jackson.databind.node.ArrayNode;
  import com.fasterxml.jackson.databind.node.ObjectNode;
  public class JacksonTester {
     public static void main(String args[]){
        JacksonTester tester = new JacksonTester();
        try {
           ObjectMapper mapper = new ObjectMapper();
           JsonNode rootNode = mapper.createObjectNode();
           JsonNode marksNode = mapper.createArrayNode();
           ((ArrayNode)marksNode).add(100);
           ((ArrayNode)marksNode).add(90);
           ((ArrayNode)marksNode).add(85);
           ((ObjectNode) rootNode).put("name", "Mahesh Kumar");
           ((ObjectNode) rootNode).put("age", 21);
           ((ObjectNode) rootNode).put("verified", false);
           ((ObjectNode) rootNode).put("marks",marksNode);
           mapper.writeValue(new File("student.json"), rootNode);
           rootNode = mapper.readTree(new File("student.json"));
           Student student = mapper.treeToValue(rootNode, Student.class);
           System.out.println("Name: "+ student.getName());
           System.out.println("Age: " + student.getAge());
           System.out.println("Verified: " + (student.isVerified() ? "Yes":"No"));
           System.out.println("Marks: "+Arrays.toString(student.getMarks()));
        } catch (JsonParseException e) {
           e.printStackTrace();
        } catch (JsonMappingException e) {
           e.printStackTrace();
        } catch (IOException e) {
           e.printStackTrace();
        }
     }
  }
  class Student {
     String name;
     int age;
     boolean verified;
     int[] marks;
     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 boolean isVerified() {
        return verified;
     }
     public void setVerified(boolean verified) {
        this.verified = verified;
     }
     public int[] getMarks() {
        return marks;
     }
     public void setMarks(int[] marks) {
        this.marks = marks;
     }
  }
  
  

  验证结果

  使用 javac 编译器编译类，如下所示：

  
  C:\Jackson_WORKSPACE>javac JacksonTester.java
  

  现在运行 JacksonTester 以查看结果：

  
  C:\Jackson_WORKSPACE>java JacksonTester
  

  验证输出

  
  Name: Mahesh Kumar
  Age: 21
  Verified: No
  Marks: [ 100 90 85 ]