Jackson ObjectMapper类使用解析

Posted 2020-08-01

/**
*   Jackson ObjectMapper类
*/
//ObjectMapper类是Jackson库的主要类。它提供一些功能将转换成Java对象匹配JSON结构，反之亦然。它使用JsonParser和JsonGenerator的实例实现JSON实际的读/写。
//以下是org.codehaus.jackson.map.ObjectMapper类的声明：

public class ObjectMapper
   extends ObjectCodec
      implements Versioned
// 演示实例：
 import java.io.IOException;
import org.codehaus.jackson.JsonParseException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.SerializationConfig;

public class JacksonTester {
   public static void main(String args[]){
      ObjectMapper mapper = new ObjectMapper();
      String jsonString = "{\"name\":\"Mahesh\", \"age\":21}";

      //map json to student
      try {
         Student student = mapper.readValue(jsonString, Student.class);
         System.out.println(student);
         mapper.enable(SerializationConfig.Feature.INDENT_OUTPUT);
         //把对象转成json string类型的
         jsonString = mapper.writeValueAsString(student);
         System.out.println(jsonString);

      } 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+ " ]";
   }    
}

//输出结果
Student [ name: Mahesh, age: 21 ]
{
  "name" : "Mahesh",
  "age" : 21
}