树到 Java 对象(Tree to Java Objects)
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2023-12-01
在这个例子中,我们使用JsonNode创建了一个Tree,并将其写入json文件并读回树,然后将其转换为Student对象。
在C:\》Jackson_WORKSPACE创建名为C:\》Jackson_WORKSPACE的java类文件。
File: 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;
}
}
Verify the result
使用javac编译器编译类,如下所示:
C:\Jackson_WORKSPACE>javac JacksonTester.java
现在运行jacksonTester查看结果:
C:\Jackson_WORKSPACE>java JacksonTester
验证输出
Name: Mahesh Kumar
Age: 21
Verified: No
Marks: [ 100 90 85 ]