ajax05 jackson一般运用

发布时间：2020-12-16 02:08:21 所属栏目：百科来源：网络整理

导读：Jackson可以轻松的将Java对象转换成json对象和xml文档，同样也可以将json、xml转换成Java对象。 1.创建动态web工程。 2.编写modle类 package org.itat.zttc.model;public class Person {private int id;private String name;private double salary;private i

Jackson可以轻松的将Java对象转换成json对象和xml文档，同样也可以将json、xml转换成Java对象。

1.创建动态web工程。

2.编写modle类

package org.itat.zttc.model;


public class Person {
	private int id;
	private String name;
	private double salary;
	private int age;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public double getSalary() {
		return salary;
	}
	public void setSalary(double salary) {
		this.salary = salary;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public Person(int id,String name,double salary,int age) {
		super();
		this.id = id;
		this.name = name;
		this.salary = salary;
		this.age = age;
	}
	
	public Person() {
	}
}

package org.itat.zttc.model;

import java.util.ArrayList;
import java.util.List;

public class Group {
	private int id;
	private String name;
	List<User> users;
	
	public void addUser(User u) {
		if(users==null) {
			users = new ArrayList<User>();
		}
		users.add(u);
	}
	
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Group(int id,String name) {
		super();
		this.id = id;
		this.name = name;
	}
	
	public Group() {
	}

}

package org.itat.zttc.model;

public class User {
	private int id;
	private String username;
	private String password;
	private Group group;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
	public Group getGroup() {
		return group;
	}
	public void setGroup(Group group) {
		this.group = group;
	}
	
	public User() {
	}
	
	public User(int id,String username,String password,Group group) {
		super();
		this.id = id;
		this.username = username;
		this.password = password;
		this.group = group;
	}
	
	public User(int id,String password) {
		super();
		this.id = id;
		this.username = username;
		this.password = password;
	}
}

3.导入jackson包

4.编写测试类

package org.itat.zttc.test;


import java.io.IOException;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import org.itat.zttc.model.Group;
import org.itat.zttc.model.User;
import org.itat.zttc.util.JsonUtil;
import org.junit.Test;

import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

public class TestJaskson {

	@Test
	public void test01() {
		StringWriter out = new StringWriter();
		JsonGenerator jg = null;
		try {
			//1、创建JsonFactory
			JsonFactory jf = new JsonFactory();
			//2、创建JsonGenerator
			jg = jf.createJsonGenerator(out);
			//使用一种相对漂亮的格式输出
			jg.useDefaultPrettyPrinter();
			//3、创建ObjectMapper,通过ObjectMapper来写对象
			User u = new User(1,"劳动法","123",new Group(1,"财务处"));
			ObjectMapper mapper = new ObjectMapper();
			mapper.writeValue(jg,u);
			System.out.println(out.toString());
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally {
			try {
				if(jg!=null) jg.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}
	
	@Test
	public void test02() {
		StringWriter out = new StringWriter();
		JsonGenerator jg = null;
		try {
			//1、创建JsonFactory
			JsonFactory jf = new JsonFactory();
			//2、创建JsonGenerator
			jg = jf.createJsonGenerator(out);
			//使用一种相对漂亮的格式输出
//			jg.useDefaultPrettyPrinter();
			//3、创建ObjectMapper,通过ObjectMapper来写对象
			List<User> us = new ArrayList<User>();
			User u = new User(1,"财务处"));
			us.add(u);
			u = new User(2,"猪八戒","财务处"));
			us.add(u);
			u = new User(3,"张学友",new Group(2,"教务处"));
			us.add(u);
			ObjectMapper mapper = new ObjectMapper();
			mapper.writeValue(jg,us);
			System.out.println(out.toString());
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally {
			try {
				if(jg!=null) jg.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}
	
	@Test
	public void test02_1() {
		List<User> us = new ArrayList<User>();
		User u = new User(1,"财务处"));
		us.add(u);
		u = new User(2,"财务处"));
		us.add(u);
		u = new User(3,"教务处"));
		us.add(u);
		System.out.println(JsonUtil.getInstance().obj2json(us));
	}
	
	@Test
	public void test03() {
		try {
			String json = "{"id":1,"username":"杂货","password":"123","group":{"id":1,"name":"财务处"}}";
			ObjectMapper mapper = new ObjectMapper();
			User u = mapper.readValue(json,User.class);
			System.out.println(u.getId()+","+u.getUsername()+","+u.getGroup().getName());
		} catch (JsonParseException e) {
			e.printStackTrace();
		} catch (JsonMappingException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	
	@Test
	public void test04() {
		try {
			String json = "[{"id":1,"username":"劳动法","name":"财务处"}},{"id":2,"username":"猪八戒",{"id":3,"username":"张学友","group":{"id":2,"name":"教务处"}}]";
			ObjectMapper mapper = new ObjectMapper();
			//在把json转换为list的时候，不能直接存储Bean对象，list中存储的是Map对象
			/*List<User> us = mapper.readValue(json,List.class);
			for(User u:us) {
				System.out.println(u.getUsername());
			}*/
			/**
			 * 所以的json都是通过map来存储的，不会直接存储bean，但是在开发中，把字符串转换为对象
			 * 一般只会对单个的对象转换，很少会用到对对象的完全转换
			 */
			List<Map<String,Object>> us = mapper.readValue(json,List.class);
			for(Map<String,Object> m:us) {
				System.out.println(m.get("id"));
				System.out.println(m.get("group"));
			}
		} catch (JsonParseException e) {
			e.printStackTrace();
		} catch (JsonMappingException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}

	}
	
	@Test
	public void test05() {
		try {
			String json = "[{"id":1,"name":"教务处"}}]";
			ObjectMapper mapper = new ObjectMapper();
			/*
			 * 在Jaskson中提供了一种基于节点的读取方法
			 */
			JsonNode node = mapper.readTree(json);
			//判断这个节点是否是数组
			System.out.println(node.isArray());
			System.out.println(node.size());
			System.out.println(node.get(0).get("username"));
			System.out.println(node.get(0).get("group").get("name"));
		} catch (JsonParseException e) {
			e.printStackTrace();
		} catch (JsonMappingException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}

	}
	

}

5.编写工具类。

package org.itat.zttc.util;


import java.io.IOException;
import java.io.StringWriter;

import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JsonUtil {
	private static JsonUtil ju;
	private static JsonFactory jf;
	private static ObjectMapper mapper;
	private JsonUtil(){}
	
	public static JsonUtil getInstance() {
		if(ju==null) ju = new JsonUtil();
		return ju;
	}
	
	public static ObjectMapper getMapper() {
		if(mapper==null) {
			mapper = new ObjectMapper();
		}
		return mapper;
	}
	
	public static JsonFactory getFactory() {
		if(jf==null) jf = new JsonFactory();
		return jf;
	}
	
	public String obj2json(Object obj) {
		JsonGenerator jg = null;
		try {
			jf = getFactory();
			mapper = getMapper();
			StringWriter out = new StringWriter();
			jg = jf.createJsonGenerator(out);
			mapper.writeValue(jg,obj);
			return out.toString();
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				if(jg!=null) jg.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		return null;
	}
	
	public Object json2obj(String json,Class<?> clz) {
		try {
			mapper = getMapper();
			return mapper.readValue(json,clz);
		} catch (JsonParseException e) {
			e.printStackTrace();
		} catch (JsonMappingException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return null;
	}
}

6.运行程序，察看运行结果

（编辑：李大同）

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