jackson学习之三：常用API操作

import com.fasterxml.jackson.databind.JsonNode;

import com.fasterxml.jackson.databind.ObjectMapper;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import java.io.File;

import java.net.URL;

import java.text.SimpleDateFormat;

import java.util.*;

public class SimpleDemo {

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

public static void main(String[] args) throws Exception {

ObjectMapper mapper = new ObjectMapper();

logger.info(“以下是序列化操作”);

// 对象 -> 字符串

TwitterEntry twitterEntry = new TwitterEntry();

twitterEntry.setId(123456L);

twitterEntry.setFromUserId(101);

twitterEntry.setToUserId(102);

twitterEntry.setText(“this is a message for serializer test”);

twitterEntry.setLanguageCode(“zh”);

String jsonStr = mapper.writeValueAsString(twitterEntry);

logger.info(“序列化的字符串：{}”, jsonStr);

// 对象 -> 文件

mapper.writeValue(new File(“twitter.json”), twitterEntry);

// 对象 -> byte数组

byte[] array = mapper.writeValueAsBytes(twitterEntry);

logger.info("\n\n以下是反序列化操作");

// 字符串 -> 对象

String objectJsonStr = “{\n” +

" “id”:1125687077,\n" +

" “text”:"@stroughtonsmith You need to add a \“Favourites\” tab to TC/iPhone. Like what TwitterFon did. I can’t WAIT for your Twitter App!! Any ETA?",\n" +

" “fromUserId”:855523, \n" +

" “toUserId”:815309,\n" +

" “languageCode”:“en”\n" +

“}”;

TwitterEntry tFromStr = mapper.readValue(objectJsonStr, TwitterEntry.class);

logger.info(“从字符串反序列化的对象：{}”, tFromStr);

// 文件 -> 对象

TwitterEntry tFromFile = mapper.readValue(new File(“twitter.json”), TwitterEntry.class);

logger.info(“从文件反序列化的对象：{}”, tFromStr);

// byte数组 -> 对象

TwitterEntry tFromBytes = mapper.readValue(array, TwitterEntry.class);

logger.info(“从byte数组反序列化的对象：{}”, tFromBytes);

// 字符串网络地址 -> 对象

String testJsonDataUrl = “https://raw.githubusercontent.com/zq2599/blog_demos/master/files/twitteer_message.json”;

TwitterEntry tFromUrl = mapper.readValue(new