Java对象与JSON互转的示例代码详解

import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.json.JSONObject;

/**
* Json工具类，实现了实体类和Json数据格式之间的互转功能 使用实例：<br>
*/
public class JsonUtils {
    /**
     * 将一个实体类对象转换成Json数据格式
     * 
     * @param bean
     *            需要转换的实体类对象
     * @return 转换后的Json格式字符串
     */
    private static String beanToJson(Object bean) {
        StringBuilder json = new StringBuilder();
        json.append("{");
        PropertyDescriptor[] props = null;
        try {
            props = Introspector.getBeanInfo(bean.getClass(), Object.class)
                    .getPropertyDescriptors();
        } catch (IntrospectionException e) {
        }
        if (props != null) {
            for (int i = 0; i < props.length; i++) {
                try {
                    String name = objToJson(props[i].getName());
                    String value = objToJson(props[i].getReadMethod()
                            .invoke(bean));
                    json.append(name);
                    json.append(":");
                    json.append(value);
                    json.append(",");
                } catch (Exception e) {
                }
            }
            json.setCharAt(json.length() - 1, '}');
        } else {
            json.append("}");
        }
        return json.toString();
    }


    /**
     * 将一个List对象转换成Json数据格式返回
     * 
     * @param list
     *            需要进行转换的List对象
     * @return 转换后的Json数据格式字符串
     */
    private static String listToJson(List<?> list) {
        StringBuilder json = new StringBuilder();
        json.append("[");
        if (list != null && list.size() > 0) {
            for (Object obj : list) {
                json.append(objToJson(obj));
                json.append(",");
            }
            json.setCharAt(json.length() - 1, ']');
        } else {
            json.append("]");
        }
        return json.toString();
    }

    /**
     * 将一个对象数组转换成Json数据格式返回
     * 
     * @param array
     *            需要进行转换的数组对象
     * @return 转换后的Json数据格式字符串
     */
    private static String arrayToJson(Object[] array) {
        StringBuilder json = new StringBuilder();
        json.append("[");
        if (array != null && array.length > 0) {
            for (Object obj : array) {
                json.append(objToJson(obj));
                json.append(",");
            }
            json.setCharAt(json.length() - 1, ']');
        } else {
            json.append("]");
        }
        return json.toString();
    }

    /**
     * 将一个Map对象转换成Json数据格式返回
     * 
     * @param map
     *            需要进行转换的Map对象
     * @return 转换后的Json数据格式字符串
     */
    private static String mapToJson(Map<?, ?> map) {
        StringBuilder json = new StringBuilder();
        json.append("{");
        if (map != null && map.size() > 0) {
            for (Object key : map.keySet()) {
                json.append(objToJson(key));
                json.append(":");
                json.append(objToJson(map.get(key)));
                json.append(",");
            }
            json.setCharAt(json.length() - 1, '}');
        } else {
            json.append("}");
        }
        return json.toString();
    }

    /**
     * 将一个Set对象转换成Json数据格式返回
     * 
     * @param set
     *            需要进行转换的Set对象
     * @return 转换后的Json数据格式字符串
     */
    private static String setToJson(Set<?> set) {
        StringBuilder json = new StringBuilder();
        json.append("[");
        if (set != null && set.size() > 0) {
            for (Object obj : set) {
                json.append(objToJson(obj));
                json.append(",");
            }
            json.setCharAt(json.length() - 1, ']');
        } else {
            json.append("]");
        }
        return json.toString();
    }

    private static String stringToJson(String s) {
        if (s == null) {
            return "";
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < s.length(); i++) {
            char ch = s.charAt(i);
            switch (ch) {
            case '"':
                sb.append("\"");
                break;
            case '\':
                sb.append("\\");
                break;
            case '':
                sb.append("\b");
                break;
            case '':
                sb.append("\f");
                break;
            case '
':
                sb.append("\n");
                break;
            case '
':
                sb.append("\r");
                break;
            case '	':
                sb.append("\t");
                break;
            case '/':
                sb.append("\/");
                break;
            default:
                if (ch >= 'u0000' && ch <= 'u001F') {
                    String ss = Integer.toHexString(ch);
                    sb.append("\u");
                    for (int k = 0; k < 4 - ss.length(); k++) {
                        sb.append('0');
                    }
                    sb.append(ss.toUpperCase());
                } else {
                    sb.append(ch);
                }
            }
        }
        return sb.toString();
    }

    public static String objToJson(Object obj) {
        StringBuilder json = new StringBuilder();
        if (obj == null) {
            json.append("""");
        } else if (obj instanceof Number) {
            Number num = (Number)obj;
            json.append(num.toString());
        } else if (obj instanceof Boolean) {
            Boolean bl = (Boolean)obj;
            json.append(bl.toString());
        } else if (obj instanceof String) {
            json.append(""").append(stringToJson(obj.toString())).append(""");
        } else if (obj instanceof Object[]) {
            json.append(arrayToJson((Object[]) obj));
        } else if (obj instanceof List) {
            json.append(listToJson((List) obj));
        } else if (obj instanceof Map) {
            json.append(mapToJson((Map) obj));
        } else if (obj instanceof Set) {
            json.append(setToJson((Set) obj));
        } else {
            json.append(beanToJson(obj));
        }
        return json.toString();
    }
    
    /**
      * @Title: json2Map
      * @Creater: chencc <br>
      * @Date: 2011-3-28 <br>
      * @Description: TODO转化json2map
      * @param @param jsonString
      * @param @return
      * @return Map<String,Object>
      * @throws
     */
    @SuppressWarnings("unchecked")
    public static Map<String, Object> json2Map(String jsonString) {
        
        Map<String, Object> map = new HashMap<String, Object>();
        try {
            if(null != jsonString && !"".equals(jsonString)){
                JSONObject jsonObject = new JSONObject(jsonString);
            
                Iterator keyIter = jsonObject.keys();
                String key = "";
                Object value = null;
            
                while (keyIter.hasNext()) {
                    key = (String) keyIter.next();
                    value = jsonObject.get(key);
                    map.put(key, value);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return map;
    }
    
    //测试方法
    public static void main(String[] args) {
        Map<String,Object> params = new HashMap<String,Object>();
        params.put("callId123", Integer.valueOf(1000));
        Map retMap = new HashMap();
        retMap.put("params", params);
        retMap.put("result", true);
        List ls = new ArrayList();
        ls.add(new HashMap());
        ls.add("hello world!!");
        ls.add(new String[4]);
        retMap.put("list", ls);
        
        String[] strArray = new String[10];
        strArray[1]="first";
        strArray[2]="2";
        strArray[3]="3";
        System.out.println("Boolean:"+JsonUtils.objToJson(true));
        System.out.println("Number:"+JsonUtils.objToJson(23.3));
        System.out.println("String:"+JsonUtils.objToJson("sdhfsjdgksdlkjfk"sd,!#%$^&*#(*@&*%&*$fsdfsdfsdf"));
        System.out.println("Map :"+JsonUtils.objToJson(retMap));
        System.out.println("List:"+JsonUtils.objToJson(ls));
        System.out.println("Array:"+JsonUtils.objToJson(strArray));
        
        String json = JsonUtils.objToJson(retMap);
        Map r = JsonUtils.json2Map(json);
        System.out.println(r.get("callId123"));
        
        
    }
}

import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.TimeZone;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;
import net.sf.json.JsonConfig;
import net.sf.json.util.CycleDetectionStrategy;
import net.sf.json.util.PropertyFilter;

import com.fasterxml.jackson.annotation.JsonInclude.Include;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JsonUtil {
    
    
    private static ObjectMapper objectMapper = null;
    /**
     * JSON初始化
     */
    static {
        objectMapper = new ObjectMapper();  
        //设置为中国上海时区  
        objectMapper.setTimeZone(TimeZone.getTimeZone("GMT+8"));  
        //空值不序列化  
        objectMapper.setSerializationInclusion(Include.NON_NULL);  
        //反序列化时，属性不存在的兼容处理  
        objectMapper.getDeserializationConfig().withoutFeatures(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);  
        //序列化时，日期的统一格式  
        objectMapper.setDateFormat(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"));  

        objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);  
        
    } 
    
    
    /**
     * 把对象转换成为Json字符串
     *
     * @param obj
     * @return
     */
    public static String convertObjectToJson(Object obj) {
        if (obj == null) {
//                throw new IllegalArgumentException("对象参数不能为空。");
            return null;
        }
        try {
            return objectMapper.writeValueAsString(obj);

        }  catch (IOException e) {
            e.printStackTrace();
        }
        return null;

    }
    /**
     *  把json字符串转成Object对象
     * @param jsonString
     * @return T
     */
    public static <T> T parseJsonToObject(String jsonString, Class<T> valueType) {
        
        if(jsonString == null || "".equals((jsonString))){
            return null;
        }
        try {
            return objectMapper.readValue(jsonString, valueType);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }
    /**
     *  把json字符串转成List对象
     * @param jsonString
     * @return List<T>
     */
    @SuppressWarnings("unchecked")
    public static <T> List<T> parseJsonToList(String jsonString,Class<T> valueType) {
        
        if(jsonString == null || "".equals((jsonString))){
            return null;
        }
        
        List<T> result = new ArrayList<T>();
        try {
            List<LinkedHashMap<Object, Object>> list = objectMapper.readValue(jsonString, List.class);
            
            for (LinkedHashMap<Object, Object> map : list) {
                
                String jsonStr = convertObjectToJson(map);
                
                T t = parseJsonToObject(jsonStr, valueType);
                
                result.add(t);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }
    /**
     * JSON处理含有嵌套关系对象，避免出现异常：net.sf.json.JSONException: There is a cycle in the hierarchy的方法
     * 注意：这样获得到的字符串中，引起嵌套循环的属性会置为null
     *
     * @param obj
     * @return
     */
    public static JSONObject getJsonObject(Object obj) {

        JsonConfig jsonConfig = new JsonConfig();
        jsonConfig.setCycleDetectionStrategy(CycleDetectionStrategy.LENIENT);
        jsonConfig.setJsonPropertyFilter(new PropertyFilter() {
            
            @Override
            public boolean apply(Object source, String name, Object value) {
                if(value==null){
                    return true;
                }
                return false;
            }
        });
        return JSONObject.fromObject(obj, jsonConfig);
    }
    /**
     * JSON处理含有嵌套关系对象，避免出现异常：net.sf.json.JSONException: There is a cycle in the hierarchy的方法

     * 注意：这样获得到的字符串中，引起嵌套循环的属性会置为null
     *
     * @param obj
     * @return
     */
    public static JSONArray getJsonArray(Object obj) {

        JsonConfig jsonConfig = new JsonConfig();
        jsonConfig.setCycleDetectionStrategy(CycleDetectionStrategy.LENIENT);

        return JSONArray.fromObject(obj, jsonConfig);
    }
    /**
     * 解析JSON字符串成一个MAP
     *
     * @param jsonStr json字符串，格式如： {dictTable:"BM_XB",groupValue:"分组值"}
     * @return
     */
    public static Map<String, Object> parseJsonStr(String jsonStr) {

        Map<String, Object> result = new HashMap<String, Object>();

        JSONObject jsonObj = JsonUtil.getJsonObject(jsonStr);

        for (Object key : jsonObj.keySet()) {
            result.put((String) key, jsonObj.get(key));
        }
        return result;
    }

}