java对象转换成json

package com.bjs.acrosstime.utils;

import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.Map;

import org.apache.log4j.Logger;
import org.codehaus.jackson.annotate.JsonIgnore;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.type.TypeFactory;

/**
* @author Peter
*/
public class JsonUtils {

private static Logger errLogger = Logger.getLogger("error");
private static Logger apiAccessLogger = Logger.getLogger("access");
private static final String PREFIX = "apiAccessAop";

//each thread has its own ObjectMapper instance
private static ThreadLocal<ObjectMapper> objMapperLocal = new ThreadLocal<ObjectMapper>(){
@Override
public ObjectMapper initialValue(){
return new ObjectMapper();
}
};

public static String toJSON(Object value) {
String result = null;
try {
result = objMapperLocal.get().writeValueAsString(value);
} catch (Exception e) {
e.printStackTrace();
} 
// Fix null string
if ("null".equals(result)) {
result = null;
}
return result;
}

public static <T> T toT(String jsonString, Class<T> clazz) {
try {
return objMapperLocal.get().readValue(jsonString, clazz);
} catch (Exception e) {
errLogger.error("toT error: "+ jsonString,e);
} 
return null;
}

public static <T> List<T> toTList(String jsonString, Class<T> clazz) {
try {
return objMapperLocal.get().readValue(jsonString, TypeFactory.collectionType(List.class, clazz));
} catch (Exception e) {
errLogger.error("toTList error: "+ jsonString,e);
} 
return null;
}

@SuppressWarnings("unchecked")
public static Map<String, Object> toMap(String jsonString) {
return toT(jsonString, Map.class);
}

public static void main(String[] args) {
Message msg1 = new Message();
msg1.uid = "1";
msg1.opr_time = new Date();
msg1.content = "hello world---1";

Message msg2 = new Message();
msg2.uid = "2";
msg2.opr_time = new Date();
msg2.content = "hello world---2";

List<Message> list = new ArrayList<Message>();
list.add(msg1);
list.add(msg2);
final String json = toJSON(list);
System.out.println(json);

//String l = "[{\"opr_time\":\"2012-05-12 12:33:22\",\"uid\":\"akun\",\"content\":\"\u5927\u5730\u9707\u7684\u4eba\u4eec\u5b89\u606f\u5427\"},{\"opr_time\":\"2012-05-12 12:33:25\",\"uid\":\"requelqi\",\"content\":\"\u6211\u56de\u5bb6\u4e86\"},{\"opr_time\":\"2012-05-12 12:37:25\",\"uid\":\"stone\",\"content\":\"\u4eca\u5929\u4e0d\u65b9\u4fbf\u6e38\u620f\"}]";
final List<Message> newMsg = JsonUtils.toTList(json, Message.class);
System.out.println(newMsg);
System.out.println((newMsg.get(0).uid));
}

static class Message {
String uid;
Date opr_time;
@JsonIgnore
String content;
public String getUid() {
return uid;
}
public void setUid(String uid) {
this.uid = uid;
}
public Date getOpr_time() {
return opr_time;
}
public void setOpr_time(Date opr_time) {
this.opr_time = opr_time;
}
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
}

}