/**
* 使用Jackson生成json格式字符串
*
* @author archie2010 since 2011-4-26下午05:59:46
*/
public class JacksonTest {

private static JsonGenerator jsonGenerator = null;
private static ObjectMapper objectMapper = null;
private static User user = null;

/**
* 转化实体为json字符串
* @throws IOException
*/
public static void writeEntity2Json() throws IOException{
System.out.println("使用JsonGenerator转化实体为json串-------------");
//writeObject可以转换java对象，eg:JavaBean/Map/List/Array等
jsonGenerator.writeObject(user);
System.out.println();
System.out.println("使用ObjectMapper-----------");
//writeValue具有和writeObject相同的功能
objectMapper.writeValue(System.out, user);
}
/**
* 转化Map为json字符串
* @throws JsonGenerationException
* @throws JsonMappingException
* @throws IOException
*/
public static void writeMap2Json() throws JsonGenerationException, JsonMappingException, IOException{
System.out.println("转化Map为字符串--------");
Map<String, Object> map=new HashMap<String, Object>();
map.put("uname", user.getUname());
map.put("upwd", user.getUpwd());
map.put("USER", user);
objectMapper.writeValue(System.out, map);
}
/**
* 转化List为json字符串
* @throws IOException
* @throws JsonMappingException
* @throws JsonGenerationException
*/
public static void writeList2Json() throws IOException{
List<User> userList=new ArrayList<User>();
userList.add(user);

User u=new User();
u.setUid(10);
u.setUname("archie");
u.setUpwd("123");
userList.add(u);
objectMapper.writeValue(System.out, userList);

objectMapper.writeValue(System.out, userList);
}
public static void main(String[] args) {
user = new User();
user.setUid(5);
user.setUname("tom");
user.setUpwd("123");
user.setNumber(3.44);
objectMapper = new ObjectMapper();
try {
jsonGenerator = objectMapper.getJsonFactory().createJsonGenerator(System.out, JsonEncoding.UTF8);
//writeEntity2Json();
//writeMap2Json();
writeList2Json();
} catch (IOException e) {

e.printStackTrace();

}
}
}

StringWriter writer = new StringWriter();
ObjectMapper mapper = new ObjectMapper();
try {
mapper.writeValue(writer, hMap);
} catch (JsonGenerationException e) {
e.printStackTrace();
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

response.setContentType("text/html;charset=UTF-8");
PrintWriter out= response.getWriter();

out.print(writer.toString());