TwitterEntry tFromFile = mapper.readValue(new File(“twitter.json”), TwitterEntry.class);
- byte数组转对象：
TwitterEntry tFromBytes = mapper.readValue(array, TwitterEntry.class);
- 字符串网络地址转对象：
String testJsonDataUrl = “https://raw.githubusercontent.com/zq2599/blog_demos/master/files/twitteer_message.json”;
TwitterEntry tFromUrl = mapper.readValue(new URL(testJsonDataUrl), TwitterEntry.class);
集合序列化- HashMap转字符串：
String mapJsonStr = mapper.writevalueAsString(map);
集合反序列化- 字符串转HashMap：
Map
- 如果您不想使用XXX.class来做反序列化，也能使用JsonNode来操作：
JsonNode jsonNode = mapper.readTree(mapJsonStr);
String name = jsonNode.get(“name”).asText();
int age = jsonNode.get(“age”).asInt();
String city = jsonNode.get(“addr”).get(“city”).asText();
String street = jsonNode.get(“addr”).get(“street”).asText();
时间字段格式化- 对于Date字段，默认的反序列化是时间戳，可以修改配置：
mapper.setDateFormat(new SimpleDateFormat(“yyyy-MM-dd hh:mm:ss”));
dateMapStr = mapper.writevalueAsString(dateMap);
JSON数组的反序列化假设jsonArrayStr是个json数组格式的字符串：
- JSON数组转对象数组：
TwitterEntry[] twitterEntryArray = mapper.readValue(jsonArrayStr, TwitterEntry[].class);
- JSON数组转对象集合(ArrayList)：
List twitterEntryList = mapper.readValue(jsonArrayStr, new TypeReference() {});
- 上述所有常用API用法的完整代码如下：
package com.bolingcavalry.jacksondemo.databind;
import com.bolingcavalry.jacksondemo.beans.TwitterEntry;
import com.fasterxml.jackson.core.type.TypeReference;
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
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.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("nn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 URL(testJsonDataUrl), TwitterEntry.class);
logger.info(“从网络地址反序列化的对象：{}”, tFromUrl);
logger.info("nn以下是集合序列化操作");
Map
map.put(“name”, “tom”);
map.put(“age”, 11);
Map
addr.put(“city”,“深圳”);
addr.put(“street”, “粤海”);
map.put(“addr”, addr);
String mapJsonStr = mapper.writevalueAsString(map);
logger.info(“HashMap序列化的字符串：{}”, mapJsonStr);
logger.info("nn以下是集合反序列化操作");
Map
logger.info(“从字符串反序列化的HashMap对象：{}”, mapFromStr);
// JsonNode类型操作
JsonNode jsonNode = mapper.readTree(mapJsonStr);
String name = jsonNode.get(“name”).asText();
int age = jsonNode.get(“age”).asInt();
String city = jsonNode.get(“addr”).get(“city”).asText();
String street = jsonNode.get(“addr”).get(“street”).asText();
logger.info(“用JsonNode对象和API反序列化得到的数：name[{}]、age[{}]、city[{}]、street[{}]”, name, age, city, street);
// 时间类型格式
Map
dateMap.put(“today”, new Date());
String dateMapStr = mapper.writevalueAsString(dateMap);
logger.info(“默认的时间序列化：{}”, dateMapStr);
// 设置时间格式
mapper.setDateFormat(new SimpleDateFormat(“yyyy-MM-dd hh:mm:ss”));
dateMapStr = mapper.writevalueAsString(dateMap);
logger.info(“自定义的时间序列化：{}”, dateMapStr);
System.out.println(objectJsonStr);
// json数组
String jsonArrayStr = “[{n” +
" “id”:1,n" +
" “text”:“text1”,n" +
" “fromUserId”:11, n" +
" “toUserId”:111,n" +
" “languageCode”:“en”n" +
“},n” +
“{n” +
" “id”:2,n" +
" “text”:“text2”,n" +
" “fromUserId”:22, n" +
" “toUserId”:222,n" +
" “languageCode”:“zh”n" +
“},n” +
“{n” +
" “id”:3,n" +
" “text”:“text3”,n" +
" “fromUserId”:33, n" +
" “toUserId”:333,n" +
" “languageCode”:“en”n" +
“}]”;
// json数组 -> 对象数组
TwitterEntry[] twitterEntryArray = mapper.readValue(jsonArrayStr, TwitterEntry[].class);
logger.info(“json数组反序列化成对象数组：{}”, Arrays.toString(twitterEntryArray));
// json数组 -> 对象集合
List twitterEntryList = mapper.readValue(jsonArrayStr, new TypeReference() {});
logger.info(“json数组反序列化成对象集合：{}”, twitterEntryList);
}
}
- 执行结果如下：
C:jdkbinjava.exe -javaagent:C:sofwareJetBrainsIntelliJIDEAlibidea_rt.jar=64570:C:sofwareJetBrainsIntelliJIDEAbin -Dfile.encoding=UTF-8 -classpath C:jdkjrelibcharsets.jar;C:jdkjrelibdeploy.jar;C:jdkjrelibextaccess-bridge-64.jar;C:jdkjrelibextcldrdata.jar;C:jdkjrelibextdnsns.jar;C:jdkjrelibextjaccess.jar;C:jdkjrelibextjfxrt.jar;C:jdkjrelibextlocaledata.jar;C:jdkjrelibextnashorn.jar;C:jdkjrelibextsunec.jar;C:jdkjrelibextsunjce_provider.jar;C:jdkjrelibextsunmscapi.jar;C:jdkjrelibextsunpkcs11.jar;C:jdkjrelibextzipfs.jar;C:jdkjrelibjavaws.jar;C:jdkjrelibjce.jar;C:jdkjrelibjfr.jar;C:jdkjrelibjfxswt.jar;C:jdkjrelibjsse.jar;C:jdkjrelibmanagement-agent.jar;C:jdkjrelibplugin.jar;C:jdkjrelibresources.jar;C:jdkjrelibrt.jar;D:githubblog_demosjacksondemodatabindtargetclasses;C:Users12167.m2repositorycomfasterxmljacksoncorejackson-databind2.11.0jackson-databind-2.11.0.jar;C:Users12167.m2repositorycomfasterxmljacksoncorejackson-annotations2.11.0jackson-annotations-2.11.0.jar;C:Users12167.m2repositorycomfasterxmljacksoncorejackson-core2.11.0jackson-core-2.11.0.jar;C:Users12167.m2repositoryorgslf4jslf4j-log4j121.7.25slf4j-log4j12-1.7.25.jar;C:Users12167.m2repositoryorgslf4jslf4j-api1.7.25slf4j-api-1.7.25.jar;C:Users12167.m2repositorylog4jlog4j1.2.17log4j-1.2.17.jar;C:Users12167.m2repositorycommons-iocommons-io2.7commons-io-2.7.jar;C:Users12167.m2repositoryorgapachecommonscommons-lang33.10commons-lang3-3.10.jar;D:githubblog_demosjacksondemobeanstargetclasses com.bolingcavalry.jacksondemo.databind.SimpleDemo
2020-08-28 07:53:01 INFO SimpleDemo:27 - 以下是序列化操作
2020-08-28 07:53:01 INFO SimpleDemo:38 - 序列化的字符串：{“id”:123456,“text”:“this is a message for serializer test”,“fromUserId”:101,“toUserId”:102,“languageCode”:“zh”}
2020-08-28 07:53:01 INFO SimpleDemo:47 -
以下是反序列化操作
2020-08-28 07:53:01 INFO SimpleDemo:60 - 从字符串反序列化的对象：[Tweet, id: 1125687077, 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?’, from: 855523, to: 815309, lang: en]
2020-08-28 07:53:01 INFO SimpleDemo:64 - 从文件反序列化的对象：[Tweet, id: 1125687077, 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?’, from: 855523, to: 815309, lang: en]
2020-08-28 07:53:01 INFO SimpleDemo:68 - 从byte数组反序列化的对象：[Tweet, id: 123456, text=‘this is a message for serializer test’, from: 101, to: 102, lang: zh]
2020-08-28 07:53:04 INFO SimpleDemo:74 - 从网络地址反序列化的对象：[Tweet, id: 112233445566, text=‘this is a message from zq2599’s github’, from: 201, to: 202, lang: en]
2020-08-28 07:53:04 INFO SimpleDemo:77 -
以下是集合序列化操作
2020-08-28 07:53:04 INFO SimpleDemo:90 - HashMap序列化的字符串：{“name”:“tom”,“addr”:{“city”:“深圳”,“street”:“粤海”},“age”:11}
2020-08-28 07:53:04 INFO SimpleDemo:92 -
以下是集合反序列化操作
2020-08-28 07:53:04 INFO SimpleDemo:94 - 从字符串反序列化的HashMap对象：{name=tom, addr={city=深圳, street=粤海}, age=11}
2020-08-28 07:53:04 INFO SimpleDemo:103 - 用JsonNode对象和API反序列化得到的数：name[tom]、age[11]、city[深圳]、street[粤海]
2020-08-28 07:53:04 INFO SimpleDemo:111 - 默认的时间序列化：{“today”:1598572384838}
2020-08-28 07:53:04 INFO SimpleDemo:116 - 自定义的时间序列化：{“today”:“2020-08-28 07:53:04”}
{
“id”:1125687077,
“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?",
“fromUserId”:855523,
“toUserId”:815309,
“languageCode”:“en”
}
2020-08-28 07:53:04 INFO SimpleDemo:145 - json数组反序列化成对象数组：[[Tweet, id: 1, text=‘text1’, from: 11, to: 111, lang: en], [Tweet, id: 2, text=‘text2’, from: 22, to: 222, lang: zh], [Tweet, id: 3, text=‘text3’, from: 33, to: 333, lang: en]]
2020-08-28 07:53:04 INFO SimpleDemo:149 - json数组反序列化成对象集合：[[Tweet, id: 1, text=‘text1’, from: 11, to: 111, lang: en], [Tweet, id: 2, text=‘text2’, from: 22, to: 222, lang: zh], [Tweet, id: 3, text=‘text3’, from: 33, to: 333, lang: en]]
Process finished with exit code 0
- 还会产生名为twitter.json的文件，内容如下：
{“id”:123456,“text”:“this is a message for serializer test”,“fromUserId”:101,“toUserId”:102,“languageCode”:“zh”}
常用配置下面是平时可能用到的自定义配置项目：
- 序列化结果格式化：
mapper.enable(SerializationFeature.INDENT_OUTPUT);
- 空对象不要抛出异常：
mapper.disable(SerializationFeature.FAIL_ON_EMPTY_BEANS);
- Date、Calendar等序列化为时间格式的字符串(如果不执行以下设置，就会序列化成时间戳格式)：
mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
- 反序列化时，遇到未知属性不要抛出异常：
mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
- 反序列化时，空字符串对于的实例属性为null：
mapper.enable(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT);
- 允许C和C++样式注释：
mapper.configure(JsonParser.Feature.ALLOW_COMMENTS, true);
