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springboot jackson自定义序列化和反序列化实例

深入理解MyBatis缓存机制

SpringBoot 如何实现自定义Redis序列化

问题

在使用RedisTemplate存储对象时，如果采用JDK默认的序列化方式，数据会出现许多编码字符，辨析度不高。比如一个空的User对象，存储到redis后如下：

这些使用JDK默认序列化方式序列化后的数据简直惨不忍睹，在使用命令行查询数据时会很头疼。

如何使数据更容易辨别呢？

一种办法是使用StringRedisTemplate，在存入redis前先将数据处理成字符串格式再存入redis，但这种方式的缺点就是每次存入数据前都要手动对非字符串数据进行处理。

另一种方法就是自定义序列化方式，只需要使用RedisTemplate就能按照自定义的序列化方式存储对象。

这里使用的是第二种方法。

环境

这里使用的SpringBoot2.0.5版本。

依赖信息：

<parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-parent</artifactId>
  <version>2.0.5.RELEASE</version>
  <relativePath/> <!-- lookup parent from repository -->
</parent>
<dependencies>
  <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
  </dependency>
  <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
  </dependency>
  <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
  </dependency>
  <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-data-redis</artifactId>
  </dependency>
  <dependency>
      <groupId>joda-time</groupId>
      <artifactId>joda-time</artifactId>
      <version>2.9.9</version>
  </dependency>
</dependencies>

SpringBoot启动类：

@SpringBootApplication
public class App {
  public static void main(String[] args) {
      SpringApplication.run(App.class);
  }
}

User实体类：

public class User implements Serializable {
  private String username;
  private String password;
  private DateTime birthday;
  public DateTime getBirthday() {
      return birthday;
  }
  public void setBirthday(DateTime birthday) {
      this.birthday = birthday;
  }
  public String getUsername() {
      return username;
  }
  public void setUsername(String username) {
      this.username = username;
  }
  public String getPassword() {
      return password;
  }
  public void setPassword(String password) {
      this.password = password;
  }
  @Override
  public String toString() {
      return "User{" +
              "username='" + username + '\'' +
              ", password='" + password + '\'' +
              ", birthday=" + birthday +
              '}';
  }
}

测试类：

@RunWith(SpringRunner.class)
@SpringBootTest
public class RedisTest {
  @Autowired
  private RedisTemplate redisTemplate;
  @Test
  public void testRedis(){
      User user = new User();
      user.setUsername("charviki");
      user.setPassword("123456");
      redisTemplate.opsForValue().set("user", user);
      User user1 = (User) redisTemplate.opsForValue().get("user");
      System.out.println(user1);
  }
}

入口点

当引入redis启动器时，SpringBoot通过RedisTemplate这个类自动帮我们配置了许多默认参数，包括redis主机，默认序列化方式等。找到RedisAutoConfiguration这个类，这个类中有如下代码：

这里使用了注解@ConditionalOnMissingBean(name = "redisTemplate")，大致意思就是如果Spring容器中没有RedisTemplate这个bean，就会返回一个默认的RedisTemplate（配置信息都在这个类里面）。

到这里就有大致的思路了，要想实现自定义redis序列化，首先定义一个返回类型为RedisTemplate的bean，并将该bean交由Spring容器管理。

实现自定义序列化

定义RedisConfig类，自定义序列化：

@Component
public class RedisConfig {
  @Bean
  public RedisTemplate<Object, Object> redisTemplate(RedisConnectionFactory redisConnectionFactory){
      RedisTemplate redisTemplate = new RedisTemplate();
      redisTemplate.setConnectionFactory(redisConnectionFactory);
      // 自定义key序列化方式,直接将String字符串直接作为redis中的key
      StringRedisSerializer stringRedisSerializer = new StringRedisSerializer();
      redisTemplate.setKeySerializer(stringRedisSerializer);
      // 自定义value序列化方式，序列化成json格式
      Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);
      redisTemplate.setValueSerializer(jackson2JsonRedisSerializer);
      return redisTemplate;
  }
}

运行测试类，程序报错，错误信息如下：

java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to cn.charviki.pojo.User

at cn.charviki.test.RedisTest.testRedis(RedisTest.java:33)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:73)
at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:83)
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:251)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

先不管错误信息，先去在redis中查看数据，如下：

也就是说数据存进去了，但是取不出来。

这个时候回去看错误信息：

java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to cn.charviki.pojo.User

看异常名也可以知道，类转换异常，即从redis中取数据后反序列化异常。

这个异常出现的原因是在序列化的时候我们没有加入类信息，取出来的时候jvm找不到类信息，无法将该json数据转换对应的类。

解决这个问题只需要在对值序列化的时候加入类信息，修改redisTemplate方法如下：

@Bean
public RedisTemplate<Object, Object> redisTemplate(RedisConnectionFactory redisConnectionFactory){
  RedisTemplate redisTemplate = new RedisTemplate();
  redisTemplate.setConnectionFactory(redisConnectionFactory);
  // 自定义key序列化方式,直接将String字符串直接作为redis中的key
  StringRedisSerializer stringRedisSerializer = new StringRedisSerializer();
  redisTemplate.setKeySerializer(stringRedisSerializer);
  // 自定义value序列化方式，序列化成json格式
  Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new 					Jackson2JsonRedisSerializer(Object.class);
  //jackson底层的序列化和反序列化使用的是ObjectMapper,我们可以通过ObjectMapper设置序列化信息
  // 设置值的默认类型，即类信息
  ObjectMapper objectMapper = new ObjectMapper();
  objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
  // 添加进序列化中
  jackson2JsonRedisSerializer.setObjectMapper(objectMapper);
  redisTemplate.setValueSerializer(jackson2JsonRedisSerializer);
  return redisTemplate;
}

再次运行测试类，控制台打印信息如下：

这里我们就实现了将对象使用json的序列化方式，但是这里会出现一个问题，就是当对象中成员变量的数据类型不是JDK中的数据类型时就会出现问题。比如说User类中有一个DateTime类型的birthday变量，这个DateTime是joda-time包下的一个日期类，在上面pom文件中已经引入了依赖。在上面测试类中我们没有为这个变量值赋值，现在让我们修改测试类：

@Test
public void testRedis(){
  User user = new User();
  user.setUsername("charviki");
  user.setPassword("123456");
  // 这里打印出dateTime，方便和redis中对比
  DateTime dateTime = new DateTime();
  System.out.println("dateTime = " + dateTime);
  user.setBirthday(dateTime);
  redisTemplate.opsForValue().set("user",user);
  User user1 = (User) redisTemplate.opsForValue().get("user");
  System.out.println(user1);
}

运行测试类，这个时候程序报错，错误信息如下：

org.springframework.data.redis.serializer.SerializationException: Could not read JSON: Unrecognized field "era" (class org.joda.time.DateTime), not marked as ignorable (2 known properties: "chronology", "millis"])
at [Source: (byte[])"["cn.charviki.pojo.User",{"username":"charviki","password":"123456","birthday":{"era":1,"dayOfMonth":16,"dayOfWeek":3,"dayOfYear":289,"year":2019,"hourOfDay":15,"minuteOfHour":30,"yearOfEra":2019,"yearOfCentury":19,"monthOfYear":10,"weekyear":2019,"centuryOfEra":20,"millisOfDay":55811047,"secondOfDay":55811,"minuteOfDay":930,"weekOfWeekyear":42,"millisOfSecond":47,"secondOfMinute":11,"zone":["org.joda.time.tz.CachedDateTimeZone",{"fixed":false,"uncachedZone":["org.joda.time.tz.DateTimeZoneBuilde"[truncated 439 bytes]; line: 1, column: 88] (through reference chain: cn.charviki.pojo.User["birthday"]->org.joda.time.DateTime["era"]); nested exception is com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "era" (class org.joda.time.DateTime), not marked as ignorable (2 known properties: "chronology", "millis"])
at [Source: (byte[])"["cn.charviki.pojo.User",{"username":"charviki","password":"123456","birthday":{"era":1,"dayOfMonth":16,"dayOfWeek":3,"dayOfYear":289,"year":2019,"hourOfDay":15,"minuteOfHour":30,"yearOfEra":2019,"yearOfCentury":19,"monthOfYear":10,"weekyear":2019,"centuryOfEra":20,"millisOfDay":55811047,"secondOfDay":55811,"minuteOfDay":930,"weekOfWeekyear":42,"millisOfSecond":47,"secondOfMinute":11,"zone":["org.joda.time.tz.CachedDateTimeZone",{"fixed":false,"uncachedZone":["org.joda.time.tz.DateTimeZoneBuilde"[truncated 439 bytes]; line: 1, column: 88] (through reference chain: cn.charviki.pojo.User["birthday"]->org.joda.time.DateTime["era"])

at org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer.deserialize(Jackson2JsonRedisSerializer.java:75)
at org.springframework.data.redis.core.AbstractOperations.deserializeValue(AbstractOperations.java:334)
at org.springframework.data.redis.core.AbstractOperations$ValueDeserializingRedisCallback.doInRedis(AbstractOperations.java:60)
at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:224)
at org.springframework.data.redis.core.RedisTemplate.execute(RedisTemplate.java:184)
at org.springframework.data.redis.core.AbstractOperations.execute(AbstractOperations.java:95)
at org.springframework.data.redis.core.DefaultValueOperations.get(DefaultValueOperations.java:48)
at cn.charviki.test.RedisTest.testRedis(RedisTest.java:34)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:73)
at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:83)
at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:251)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "era" (class org.joda.time.DateTime), not marked as ignorable (2 known properties: "chronology", "millis"])
at [Source: (byte[])"["cn.charviki.pojo.User",{"username":"charviki","password":"123456","birthday":{"era":1,"dayOfMonth":16,"dayOfWeek":3,"dayOfYear":289,"year":2019,"hourOfDay":15,"minuteOfHour":30,"yearOfEra":2019,"yearOfCentury":19,"monthOfYear":10,"weekyear":2019,"centuryOfEra":20,"millisOfDay":55811047,"secondOfDay":55811,"minuteOfDay":930,"weekOfWeekyear":42,"millisOfSecond":47,"secondOfMinute":11,"zone":["org.joda.time.tz.CachedDateTimeZone",{"fixed":false,"uncachedZone":["org.joda.time.tz.DateTimeZoneBuilde"[truncated 439 bytes]; line: 1, column: 88] (through reference chain: cn.charviki.pojo.User["birthday"]->org.joda.time.DateTime["era"])
at com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException.from(UnrecognizedPropertyException.java:60)
at com.fasterxml.jackson.databind.DeserializationContext.handleUnknownProperty(DeserializationContext.java:822)
at com.fasterxml.jackson.databind.deser.std.StdDeserializer.handleUnknownProperty(StdDeserializer.java:1152)
at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownProperty(BeanDeserializerBase.java:1589)
at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownVanilla(BeanDeserializerBase.java:1567)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:294)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:151)
at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:127)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:288)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:151)
at com.fasterxml.jackson.databind.jsontype.impl.AsArrayTypeDeserializer._deserialize(AsArrayTypeDeserializer.java:116)
at com.fasterxml.jackson.databind.jsontype.impl.AsArrayTypeDeserializer.deserializeTypedFromAny(AsArrayTypeDeserializer.java:71)
at com.fasterxml.jackson.databind.deser.std.UntypedObjectDeserializer$Vanilla.deserializeWithType(UntypedObjectDeserializer.java:712)
at com.fasterxml.jackson.databind.deser.impl.TypeWrappedDeserializer.deserialize(TypeWrappedDeserializer.java:68)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4013)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3129)
at org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer.deserialize(Jackson2JsonRedisSerializer.java:73)
... 37 more

跟前面一样先查看redis中的数据：

查看控制台打印的DataTime数据：

对比控制台数据和redis中的数据，redisTemplate将DataTime使用默认的json序列化后，多了许多字段。

再看报错信息，问题同样出在反序列化上。从报错信息中我们可以看出，在反序列化的时候找不到相应的字段。这里的解决版本是实现针对DataTime类型的序列化和反序列化器，注册到ObjectMapper中，实现对json序列化器的扩展。

先自定义序列化器，这里定义序列化器JodaDateTimeJsonSerializer和反序列化器JodaDateTimeJsonDeserializer，两者都要继承JsonDeserializer并重写父类serialize()或deserialize方法。实现代码如下：

// JodaDateTimeJsonSerializer.java
public class JodaDateTimeJsonSerializer extends JsonSerializer<DateTime> {
  @Override
  public void serialize(DateTime value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
      // 序列化
      gen.writeString(value.toString("yyyy-MM-dd HH:mm:ss"));
  }
}

// JodaDateTimeJsonDeserializer.java
public class JodaDateTimeJsonDeserializer extends JsonDeserializer<DateTime> {
  @Override
  public DateTime deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {
      String dateString = p.readValueAs(String.class);
      DateTimeFormatter dateTimeFormatter = DateTimeFormat.forPattern("yyyy-MM-dd HH:mm:ss");
      // 反序列化
      return DateTime.parse(dateString,dateTimeFormatter);
  }
}

将自定义序列化器通过ObjectMapper注册到json序列化器中，修改redisTemplate方法如下：

@Bean
public RedisTemplate<Object, Object> redisTemplate(RedisConnectionFactory redisConnectionFactory){
  RedisTemplate redisTemplate = new RedisTemplate();
  redisTemplate.setConnectionFactory(redisConnectionFactory);
  // 自定义key序列化方式,直接将String字符串直接作为redis中的key
  StringRedisSerializer stringRedisSerializer = new StringRedisSerializer();
  redisTemplate.setKeySerializer(stringRedisSerializer);
  // 自定义value序列化方式，序列化成json格式
  Jackson2JsonRedisSerializer jackson2JsonRedisSerializer = new Jackson2JsonRedisSerializer(Object.class);
  //jackson底层的序列化和反序列化使用的是ObjectMapper,我们可以通过ObjectMapper设置序列化信息
  // 设置值的默认类型，即类信息
  ObjectMapper objectMapper = new ObjectMapper();
  objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
  // SimpleModule用于设置自定义序列化器
  SimpleModule simpleModule = new SimpleModule();
  simpleModule.addSerializer(DateTime.class,new JodaDateTimeJsonSerializer());
  simpleModule.addDeserializer(DateTime.class,new JodaDateTimeJsonDeserializer());
  objectMapper.registerModule(simpleModule);
  // 添加进json序列化器中
  jackson2JsonRedisSerializer.setObjectMapper(objectMapper);
  redisTemplate.setValueSerializer(jackson2JsonRedisSerializer);
  return redisTemplate;
}

这个时候再运行测试类就没什么问题了。

控制台打印信息如下：

redis中的数据信息如下：

网上还有一种更加简便的方法就是使用jackson提供的包，引入依赖：

<dependency>
  <groupId>com.fasterxml.jackson.datatype</groupId>
  <artifactId>jackson-datatype-joda</artifactId>
  <version>2.9.9</version>
</dependency>

这个包已经帮我们实现了关于joda-time的序列化与反序列化器，我们只需要在redisTemplate方法中将对应的SimpleModel注册到ObjectMapper中就行：

objectMapper.registerModule(new JodaModule());

这样也可以达到同样的效果。

小结

总之，想要在SpringBoot中实现redis的自定义序列化，需要自定义创建一个redisTemplate的bean，设置要使用的序列化方式。通过ObjectMapper设置一些自定义序列化信息，如反序列化所要用到的类信息等。还可以对特定的数据类型进行自定义序列化，只需要通过SimpleModel注册到相应的序列化器即可。最后再将该bean交由Spring容器管理。

以上为个人经验，希望能给大家一个参考，也希望大家多多支持编程宝库。

下一节：深入理解MyBatis缓存机制

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springboot jackson自定义序列化和反序列化实例

深入理解MyBatis缓存机制