Json 数据反序列化为Java对象

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前言：我们在项目中经常用到的是Json格式的数据，如果是将一个被Jackson转化为JSON数据格式的Java对象进行操作，我们就需要将JSON数据再反序列化为Java对象。
1、实体对象

package com.boonya.gps;

import java.io.Serializable;

import org.codehaus.jackson.annotate.JsonProperty;

public class Point implements Serializable{
	
	private static final long serialVersionUID = -8359918523259373062L;
	private double lat;
	private double lng;
	
	public double getLat() {
		return lat;
	}
	
	public Point(@JsonProperty("lat") double lat,@JsonProperty("lng") double lng) {
		this.lat = lat;
		this.lng = lng;
	}

	public void setLat(double lat) {
		this.lat = lat;
	}
	
	public double getLng() {
		return lng;
	}
	
	public void setLng(double lng) {
		this.lng = lng;
	}

	@Override
	public String toString() {
		return "Point(lat,lng)="+" {lat:"+lat+","+"lng:"+lng+"}";
	}

}

2、实现JSON数据反序列化为Java对象

package com.boonya.gps;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.JsonNode;
import org.codehaus.jackson.JsonParseException;
import org.codehaus.jackson.JsonProcessingException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.type.TypeReference;
/**
 * JSON数据反序列化为Java对象或对象集合
 * @author [email protected]
 * @date  2013-8-28
 */
public class JSONSeriaToObject {
	
	/**
	 * 对象转JSON
	 * @param obj
	 * @return
	 */
	public  String getJsonFromObject(Object obj){
		ObjectMapper om = new ObjectMapper();
		try {
			return om.writeValueAsString(obj);
		} catch (JsonGenerationException e) {
			e.printStackTrace();
		} catch (JsonMappingException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return "";
	}
	
	/**
	 * JSON发序列化为Java对象
	 * @param jsonStr
	 * @return
	 */
	public  Point  getPointByJsonString(String jsonStr){
		Point point =null;
		ObjectMapper om = new ObjectMapper();
		try {
			JsonNode node=om.readTree(jsonStr);
			point= (Point) om.readValue(node.toString(),Point.class);
		} catch (JsonParseException e) {
			e.printStackTrace();
		} catch (JsonMappingException e) {
			e.printStackTrace();
		} catch (JsonGenerationException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		System.out.println("<:success single point:>"+point.toString());
		return point;
	}
	
	/**
	 * 拼接Json数据的字符串转化为标准Json格式字符串
	 * @param str
	 * @return
	 */
	public  String  getJsonNodeStringByString(String str){
		ObjectMapper om = new ObjectMapper();
		try {
			JsonNode node=om.readTree(str);
			return node.toString();
		} catch (JsonProcessingException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return "";
	}
	
	/**
	 * JSON发序列化为Java对象集合
	 * @param jsonStr
	 * @return
	 */
	@SuppressWarnings("unchecked")
	public  List  getPointsByJsonString(String jsonStr){
		List points = new ArrayList();
		ObjectMapper om = new ObjectMapper();
		try {
			JsonNode node=om.readTree(jsonStr);
			points= (List) om.readValue(node.toString(), new TypeReference>() {});
		} catch (JsonParseException e) {
			e.printStackTrace();
		} catch (JsonMappingException e) {
			e.printStackTrace();
		} catch (JsonGenerationException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		for (int i = 0; i < points.size(); i++) {
			System.out.println("<:success index "+i+":>"+points.get(i).toString());
		}
		return points;
	}

	/**
	 * JSON数据反序列化为Java对象的测试入口
	 * @param args
	 * @throws JsonGenerationException
	 * @throws JsonMappingException
	 * @throws IOException
	 */
	public static void main(String[] args) throws JsonGenerationException,JsonMappingException, IOException {
		JSONSeriaToObject jsto=new JSONSeriaToObject();
		
		//原始数据格式
		System.out.println("----------------------------------Jackson JSON(list)  to Java  Object-----------------------------"); 
		List points = new ArrayList();
		points.add(new Point(34.2332,104.46664));
		String json=jsto.getJsonFromObject(points);
		System.out.println(json);
		//JSON序列化Java对象
		jsto.getPointsByJsonString(json);
		
		System.out.println("----------------------------------Jackson JSON(T)  to Java  Object-----------------------------");
		Point point=new Point(34.5332,104.76664);
		String json2=jsto.getJsonFromObject(point);
		System.out.println(json2);
		//JSON序列化Java对象
		jsto.getPointByJsonString(json2);
		
		//JSON序列化为Java对象
		System.out.println("----------------------------------Ping string JSON  to Java  Object-----------------------------");
		String latlngs =new String("[{\"lat\":34.232013,\"lng\":103.466002},{\"lat\":34.531939,\"lng\":103.665816}]");
		//经测试以下数据若调用getJsonFromObject是不行的会产生异常
		String json3=jsto.getJsonNodeStringByString(latlngs);
		System.out.println(json3);
		
		//JSON序列化Java对象
		jsto.getPointsByJsonString(json3);

	}

}

3、打印结果

----------------------------------Jackson JSON(list)  to Java  Object-----------------------------
[{"lat":34.2332,"lng":104.46664}]
<:success index 0:>Point(lat,lng)= {lat:34.2332,lng:104.46664}
----------------------------------Jackson JSON(T)  to Java  Object-----------------------------
{"lat":34.5332,"lng":104.76664}
<:success single point:>Point(lat,lng)= {lat:34.5332,lng:104.76664}
----------------------------------Ping string JSON  to Java  Object-----------------------------
[{"lat":34.232013,"lng":103.466002},{"lat":34.531939,"lng":103.665816}]
<:success index 0:>Point(lat,lng)= {lat:34.232013,lng:103.466002}
<:success index 1:>Point(lat,lng)= {lat:34.531939,lng:103.665816}