jackson处理json对象相关小结

jackson处理json对象相关小结 - jackyrong - ITeye技术网站

jackson处理json对象相关小结

博客分类：
• JAVA相关

java json 

在解析JSON方面，无疑JACKSON是做的最好的，下面从几个方面简单复习下。



1 JAVA 对象转为JSON

 

import java.io.File;
import java.io.IOException;
import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;

public class JacksonExample {
    public static void main(String[] args) {

    User user = new User();
    ObjectMapper mapper = new ObjectMapper();

    try {

        // convert user object to json string, and save to a file
        mapper.writeValue(new File("c:\\user.json"), user);

        // display to console
        System.out.println(mapper.writeValueAsString(user));

    } catch (JsonGenerationException e) {

        e.printStackTrace();

    } catch (JsonMappingException e) {

        e.printStackTrace();

    } catch (IOException e) {

        e.printStackTrace();

    }

  }

import java.io.File;
import java.io.IOException;
import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;

public class JacksonExample {
    public static void main(String[] args) {

	User user = new User();
	ObjectMapper mapper = new ObjectMapper();

	try {

		// convert user object to json string, and save to a file
		mapper.writeValue(new File("c:\\user.json"), user);

		// display to console
		System.out.println(mapper.writeValueAsString(user));

	} catch (JsonGenerationException e) {

		e.printStackTrace();

	} catch (JsonMappingException e) {

		e.printStackTrace();

	} catch (IOException e) {

		e.printStackTrace();

	}

  }

输出为：

{"age":29,"messages":["msg 1","msg 2","msg 3"],"name":"mkyong"}





2 JSON反序列化为JAVA对象

  

import java.io.File;
import java.io.IOException;
import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;

public class JacksonExample {
    public static void main(String[] args) {

    ObjectMapper mapper = new ObjectMapper();

    try {

        // read from file, convert it to user class
        User user = mapper.readValue(new File("c:\\user.json"), User.class);

        // display to console
        System.out.println(user);

    } catch (JsonGenerationException e) {

        e.printStackTrace();

    } catch (JsonMappingException e) {

        e.printStackTrace();

    } catch (IOException e) {

        e.printStackTrace();

    }

  }

import java.io.File;
import java.io.IOException;
import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;

public class JacksonExample {
    public static void main(String[] args) {

	ObjectMapper mapper = new ObjectMapper();

	try {

		// read from file, convert it to user class
		User user = mapper.readValue(new File("c:\\user.json"), User.class);

		// display to console
		System.out.println(user);

	} catch (JsonGenerationException e) {

		e.printStackTrace();

	} catch (JsonMappingException e) {

		e.printStackTrace();

	} catch (IOException e) {

		e.printStackTrace();

	}

  }

输出：User [age=29, name=mkyong, messages=[msg 1, msg 2, msg 3]]



3 在上面的例子中，如果要输出的JSON好看点，还是有办法的，就是使用

defaultPrettyPrintingWriter()方法，例子为：

User user = new User();
  ObjectMapper mapper = new ObjectMapper();
  System.out.println(mapper.defaultPrettyPrintingWriter().writeValueAsString(user));

 User user = new User();
   ObjectMapper mapper = new ObjectMapper();
   System.out.println(mapper.defaultPrettyPrintingWriter().writeValueAsString(user));

则输出整齐：

{

  "age" : 29,

  "messages" : [ "msg 1", "msg 2", "msg 3" ],

  "name" : "mkyong"

}