Java中关于Json对象类型和字符串类型之间互相转化的问题

Java中关于Json格式转化Object,Map,Collection类型和String类型之间的转化在我们实际项目中应用的很是普遍和广泛。最近工作的过程中也是经常有，因此,自己封装了一个JsonUtil.java类。

所需要的jar包:slf4j-jdk14-1.5.6.jar,slf4j-api-1.5.6.jar------>此两个jar包是slf4j日志jar包

jackson-annotations-2.1.1.jar，jackson-core-2.1.1.jar，jackson-databind-2.1.1.jar---->实现Json转化的依赖包。

package com.clark.util;

import java.io.IOException;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Date;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonGenerationException;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ser.FilterProvider;
import com.fasterxml.jackson.databind.ser.impl.SimpleBeanPropertyFilter;
import com.fasterxml.jackson.databind.ser.impl.SimpleFilterProvider;
import com.clark.model.User;

/*
 *
 * @author caolipeng
 * @title JsonUtil.java
 * @description 提供用于Json数据转换的静态方法
 * @version V1.0
 */
public class JsonUtil {

	private static final Logger logger = LoggerFactory.getLogger(JsonUtil.class);

	/**
	 * 性能方面 JackSon > Gson > Json 故这里决定使用JackSon 将Collection转换为Json
	 * 参数是Collection
	 *
	 * @param collection
	 */
	public static String toJson(Collection<Object> collection) {
		/*
		 * 使用Gson的方式 Gson gson = new Gson(); String json = gson.toJson(map);
		 */

		/*
		 * 使用Jackson的方式
		 */
		String json = "[]";
		ObjectMapper mapper = new ObjectMapper();
		StringWriter sw = new StringWriter();
		try {
			JsonGenerator gen = new JsonFactory().createJsonGenerator(sw);
			mapper.writeValue(gen, collection);
			gen.close();
			json = sw.toString();
		} catch (JsonGenerationException e) {
			json = "[]";
			logger.error(
					"------1------ toJson JsonGenerationException error:\n", e);

		} catch (JsonMappingException e) {
			json = "[]";
			logger.error("------2------ toJson JsonMappingException error:\n",
					e);

		} catch (IOException e) {
			json = "[]";
			logger.error("------3------ toJson IOException error:\n", e);
		}

		return json;
	}

	/**
	 * @Title: toJson
	 * @Description: 将对象转换为Json数据
	 * @param @param obj
	 * @param @return 设定文件
	 * @return String 返回类型
	 * @throws
	 */
	public static String toJson(Object obj) {
		String json = "[]";
		ObjectMapper mapper = new ObjectMapper();
		StringWriter sw = new StringWriter();
		try {
			JsonGenerator gen = new JsonFactory().createJsonGenerator(sw);
			mapper.writeValue(gen, obj);
			gen.close();

			json = sw.toString();
		} catch (JsonGenerationException e) {
			json = "[]";
			logger.error("------1------ toJson IOException error:\n", e);

		} catch (JsonMappingException e) {
			json = "[]";
			logger.error("------2------ toJson IOException error:\n", e);

		} catch (IOException e) {
			json = "[]";
			logger.error("------3------ toJson IOException error:\n", e);
		}

		return json;
	}

	/**
	 * 将MAP转为Json Map参数
	 *
	 * @param map
	 * @return
	 * @throws IOException
	 */
	public static String toJson(Map<String, Object> map) {
		String json = "[]";
		ObjectMapper mapper = new ObjectMapper();
		StringWriter sw = new StringWriter();
		try {
			JsonGenerator gen = new JsonFactory().createJsonGenerator(sw);
			mapper.writeValue(gen, map);
			gen.close();

			json = sw.toString();
		} catch (JsonGenerationException e) {
			json = "[]";
			logger.error("----1------toJson JsonGenerationException:\n" + e);
		} catch (JsonMappingException e) {
			json = "[]";
			logger.error("----2------toJson JsonMappingException:\n" + e);
		} catch (IOException e) {
			json = "[]";
			logger.error("----3------toJson IOException:\n" + e);
		}

		return json;
	}

	/**
	 * 将JSON字符串 转换为对象
	 *
	 * @author weiyuanhua
	 * @date 2010-11-18 下午02:52:13
	 * @param jsonStr
	 *            JSON字符串
	 * @param beanClass
	 *            泛型对象
	 * @param field
	 *            对象中需要忽略的属性
	 * @return
	 */
	public static Object jsonToObject(String jsonStr, Class<?> beanClass)
			throws JsonParseException, JsonMappingException, IOException {
		ObjectMapper objectMapper = new ObjectMapper();
		return objectMapper.readValue(jsonStr.getBytes(), beanClass);
	}

	public static Object jsonToObject(String jsonStr, String encoding,
			Class<?> beanClass) throws JsonParseException,
			JsonMappingException, IOException {
		ObjectMapper objectMapper = new ObjectMapper();
		return objectMapper.readValue(jsonStr.getBytes(encoding), beanClass);
	}

	public static Map<String, Object> parseJSON2Map(String jsonStr)
			throws JsonParseException, JsonMappingException, IOException {
		ObjectMapper objectMapper = new ObjectMapper();
		return objectMapper.readValue(jsonStr, Map.class);
	}

	//不需要记性属性的忽略
    public static String toJson(Object object,String filterName) {
    	ObjectMapper mapper = new ObjectMapper();
        String  json = "[]";
        try {
            FilterProvider filterProvider = new SimpleFilterProvider().addFilter(filterName, SimpleBeanPropertyFilter.serializeAllExcept());
            json = mapper.writer(filterProvider).writeValueAsString(object);
        } catch (Exception e) {
            json = "[]";
            logger.error("----1------toJson Exception:\n" + e);
        }

        return json;
    }

    /*
     *
     * @param object 需要进行json序列化的类  可以是任何复杂的类
     * @param args 需要进行过滤的属性名称 类对象名称或者一些属性名称都可以进行过滤
     * */
	public static String toJson(Object object, String[] args, String filterName) {
		String json = "[]";
		ObjectMapper mapper = new ObjectMapper();
		try {
			FilterProvider filterProvider = new SimpleFilterProvider()
					.addFilter(filterName,
							SimpleBeanPropertyFilter.serializeAllExcept(args));
			json = mapper.writer(filterProvider).writeValueAsString(object);
		} catch (Exception e) {
			json = "[]";
			logger.error("----1------toJson Exception:\n" + e);
		}

		return json;
	}

	public static void main(String[] args) {
		User user = new User(12, "aaa", "123456", new Date());
//		String result = toJson(user, "id");
		String result = toJson(user);
		System.out.println(result);
		List list = new ArrayList();
		list.add(0,"name");
		list.add(1,"favorite");
		String li = toJson(list);
		System.out.println(li);

		Map<String,String> map = new HashMap<String,String>();
		map.put("password", "123");
		map.put("name", "clark");
		map.put("call", "wowo");
		String mr = toJson(map);
		System.out.println(mr);

		Date d = new Date();
		String jsonStr = "{\"id\":23,\"name\":\"44444\"}";
		try {
			User u = (User)jsonToObject(jsonStr, User.class);
			System.out.println(u.getName());

			Map<String, Object> mapResult = parseJSON2Map(jsonStr);
			Set<String> key = mapResult.keySet();
			Iterator iter = key.iterator();
			while(iter.hasNext()){
				String k = (String) iter.next();
				System.out.println(mapResult.get(k));
			}

		} catch (JsonParseException e) {
			e.printStackTrace();
		} catch (JsonMappingException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

在应用测试中的Model类---User.java类如下：

package com.clark.model;

import java.util.Date;

public class User {
    private int id;
    private String name;
    private String password;
    private Date date;
    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 String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public Date getDate() {
        return date;
    }
    public void setDate(Date date) {
        this.date = date;
    }
    public User(int id, String name, String password, Date date) {
        super();
        this.id = id;
        this.name = name;
        this.password = password;
        this.date = date;
    }

    public User(){

    }

    @Override
    public String toString() {
        return "Id:"+this.getId()+"\n"+"name:"+this.getName()+"\n"+"password:"+this.getPassword();
    }
}