JSON的转换

1.json转对象

 

String str="{\"Name\":\"leilei\",\"age\":23}";

		
					ObjectMapper objectMapper=new ObjectMapper();
					Student st=objectMapper.readValue(str, Student.class);
					System.out.println(st.getAge());

 

 

 

 

 

public class Student {
	public String name;
	public String age;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getAge() {
		return age;
	}
	public void setAge(String age) {
		this.age = age;
	}
	

}

 

JSONObject a = new JSONObject(jsonstr);  
        JSONArray array = a.getJSONArray("StoreList");

 2.对象转JSON字符串

String s = objectMapper.writeValueAsString(obj);

 

 写的公用方法

import org.codehaus.jackson.map.ObjectMapper;
import org.json.JSONArray;
import org.json.JSONObject;


** 
	 * @Title: getBeanFromJSON 
	 * @Description: TODO(这里用一句话描述这个方法的作用) 
	 * @param @param sb    设定文件 
	 * @return void    返回类型 
	 * @throws 
	 */
	public static <T> T getBeanFromJSON(String json,Class<T> clazz,String key) {
		try {
			ObjectMapper objectMapper = new ObjectMapper();
			Object object =getObjectFromJSON(json, key);
			T t=objectMapper.readValue(object.toString(), clazz);
			return t;
		} catch (Exception e) {
			logger.error("从JSON中读取Bean报错："+e.getMessage());
			e.printStackTrace();
		}
		return null;
	}
	
	/** 
	 * @Title: getObjectFromJSON 
	 * @Description: TODO(这里用一句话描述这个方法的作用) 
	 * @param @param sb    设定文件 
	 * @return void    返回类型 
	 * @throws 
	 */
	public static Object getObjectFromJSON(String json,String key) {
		try {
			JSONObject a = new JSONObject(json);  
			Object object = a.get(key);
			return object;
		} catch (Exception e) {
			logger.error("从JSON中读取取对象报错："+e.getMessage());
			e.printStackTrace();
		}
		return null;
	}
	
	/** 
	 * @Title: getBeanFromJSON 
	 * @Description: TODO(这里用一句话描述这个方法的作用) 
	 * @param @param sb    设定文件 
	 * @return void    返回类型 
	 * @throws 
	 */
	public static <T> List<T> getBeansFromJSON(String json,Class<T> clazz,String key) {
		try {
			ObjectMapper objectMapper = new ObjectMapper();
			JSONObject a = new JSONObject(json);
			JSONArray array = a.getJSONArray(key);
			List<T> list = new ArrayList<T>();
	        for (int i = 0; i < array.length(); i++) {
				objectMapper=new ObjectMapper();
				T t = objectMapper.readValue(array.get(i).toString(), clazz);
				if(t !=null){
					list.add(t);
				}
			}
			return list;
		} catch (Exception e) {
			logger.error("从JSON中读取BeanList报错："+e.getMessage());
			e.printStackTrace();
		}
		return null;
	}

 

 

 

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

 

 

	public static <T> List<T> getBeansFromJson(String json, Class<T> clazz) throws JsonParseException, JsonMappingException, IOException {
		ObjectMapper mapper = new ObjectMapper();
		JavaType javaType = mapper.getTypeFactory().constructParametricType(List.class, clazz);
		List<T> lst = (List<T>) mapper.readValue(json, javaType);
		return lst;
	}

	public static <T> T getBeanFromJson(String json, Class<T> clazz) throws JsonParseException, JsonMappingException, IOException {
		ObjectMapper mapper = new ObjectMapper();
		T t = mapper.readValue(json, clazz);
		return t;
	}

	public static String getJosnByKey(String json, String key) throws JsonProcessingException, IOException {
		ObjectMapper mapper = new ObjectMapper();
		JsonNode root = mapper.readTree(json);
		JsonNode fields = root.get(key);
		return fields.toString();
	}

 

 

import java.util.HashMap;
import java.util.Map;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.type.TypeReference;
 
public class JsonMapExample {
    public static void main(String[] args) {
 
	String json = "{\"name\":\"mkyong\", \"age\":\"29\"}";
 
	Map<String,String> map = new HashMap<String,String>();
	ObjectMapper mapper = new ObjectMapper();
 
	try {
 
		//convert JSON string to Map
		map = mapper.readValue(json, 
		    new TypeReference<HashMap<String,String>>(){});
 
		System.out.println(map);
 
	} catch (Exception e) {
		e.printStackTrace();
	}
 
    }
}


import org.codehaus.jackson.map.ObjectMapper;
 
public class MapJsonExample {
    public static void main(String[] args) {
 
	try {
 
		ObjectMapper mapper = new ObjectMapper();
		String json = "";
 
		Map<String, String> map = new HashMap<String, String>();
		map.put("name", "mkyong");
		map.put("age", "29");
 
		//convert map to JSON string
		json = mapper.writeValueAsString(map);
 
		System.out.println(json);
 
	} catch (Exception e) {
		e.printStackTrace();
	}
 
    }
}



import org.codehaus.jackson.map.ObjectMapper;
 
public class JsonMapFileExample {
    public static void main(String[] args) {
 
	ObjectMapper mapper = new ObjectMapper();
 
	Map<String, Object> map = new HashMap<String, Object>();
	map.put("name", "mkyong");
	map.put("age", 29);
 
	List<Object> list = new ArrayList<Object>();
	list.add("msg 1");
	list.add("msg 2");
	list.add("msg 3");
 
	map.put("messages", list);
 
	try {
 
		// write JSON to a file
		mapper.writeValue(new File("c:\\user.json"), map);
 
	} catch (Exception e) {
		e.printStackTrace();
	}
    }
}

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

import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.type.TypeReference;
 
public class JsonFileMapExample {
    public static void main(String[] args) {
 
	try {
 
		ObjectMapper mapper = new ObjectMapper();
 
		// read JSON from a file
		Map<String, Object> map = mapper.readValue(
			new File("c:\\user.json"),
			new TypeReference<Map<String, Object>>() {
		});
 
		System.out.println(map.get("name"));
		System.out.println(map.get("age"));
 
		@SuppressWarnings("unchecked")
		ArrayList<String> list = (ArrayList<String>) map.get("messages");
 
		for (String msg : list) {
			System.out.println(msg);
		}
 
	} catch (Exception e) {
		e.printStackTrace();
	}
 
    }
}