jackson 使用(java jar-jackson-all-1.9.0jar自行下载)

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

 import org.codehaus.jackson.JsonFactory;
 import org.codehaus.jackson.JsonGenerator;
 import org.codehaus.jackson.JsonParser;
 import org.codehaus.jackson.map.DeserializationConfig.Feature;
 import org.codehaus.jackson.map.MappingJsonFactory;
 import org.codehaus.jackson.map.ObjectMapper;
 import org.codehaus.jackson.type.JavaType;

 public class JsonUtils {

     public static <K, V> String toJson(Map<K, V> obj) {
         String jsonString = "";
         try {
             if (obj == null) {
                 return "";
             }
             StringWriter sw = new StringWriter();
             JsonGenerator gen = new JsonFactory().createJsonGenerator(sw);
             ObjectMapper mapper = new ObjectMapper();
             mapper.writeValue(gen, obj);
             jsonString = sw.toString();
             sw.close();
         } catch (Exception ex) {
             ex.printStackTrace();
             return "";
         }

         return jsonString;
     }

     @SuppressWarnings("unchecked")
     public static Map<String, Object> toMap(String json) {
         Map<String, Object> result = new HashMap<String, Object>();
         try {
             if (json == null || json.equals("")) {
                 return null;
             }

             ObjectMapper objectMapper = new ObjectMapper();
             result = objectMapper.readValue(json, Map.class);
             if (result == null) {
                 return new HashMap<String, Object>();
             }
         } catch (Exception ex) {
             ex.printStackTrace();
         }

         return result;
     }

     public static String toJson(Object object) {
         String json = "";
         try {
             if (object == null) {
                 return "";
             }
             StringWriter sw = new StringWriter();
             JsonGenerator gen = new JsonFactory().createJsonGenerator(sw);
             ObjectMapper mapper = new ObjectMapper();

             mapper.writeValue(gen, object);

             json = sw.toString();
             sw.close();
         } catch (Exception ex) {
             ex.printStackTrace();
             json = "";
         }
         return json;
     }

     public static <T> T toObject(String json, Class<T> clazz) {
         T obj = null;
         try {
             if (json == null || json.equals("")) {
                 return null;
             }
             JsonFactory jsonFactory = new MappingJsonFactory();
             JsonParser jsonParser = jsonFactory.createJsonParser(json);
             ObjectMapper mapper = new ObjectMapper();
     mapper.configure(Feature.FAIL_ON_UNKNOWN_PROPERTIES,false);
             //mapper.getDeserializationConfig().set(Feature.FAIL_ON_UNKNOWN_PROPERTIES, false);
             obj = mapper.readValue(jsonParser, clazz);

         } catch (Exception ex) {
             ex.printStackTrace();
             obj = null;
         }
         return obj;

     }

     public static <T> List<T> toList(String json, Class<T> clazz) {
         if (json == null || json.equals("")) {
             return null;
         }
         ObjectMapper mapper = new ObjectMapper();
         mapper.configure(Feature.FAIL_ON_UNKNOWN_PROPERTIES,false);
         List<T> list = new ArrayList<T>();
         try {
             JavaType type = mapper.getTypeFactory().constructParametricType(List.class, clazz);
             list = mapper.readValue(json, type);
             return list;
         } catch (Exception e) {
             e.printStackTrace();
         }

         return list;
     }
 }