@[TOC]

一、报错详情

1、环境信息

• Spring Boot : 2.4.2
• Spring Cloud：2020.0.1
• Spring Cloud Alibaba：2021.1
• Seata:1.3.0
• mysql-connector-java：8.0.28

和报错相关的是Seata 和 mysql-connector-java的版本信息

2、Seata undo_log日志表结构

其中 log_created、log_modified字段的类型是datetime。

3、详细异常信息

在分布式全局事务执行失败进行全局回滚时，需要通过Seata 的 undoLog回滚的服务会出现报错信息，如下：

2022-08-05 18:04:03.583 ERROR 16225 --- [h_RMROLE_1_8_16] i.s.r.d.u.parser.JacksonUndoLogParser    : json decode exception, Cannot construct instance of `java.time.LocalDateTime` (no Creators, like default constructor, exist): cannot deserialize from Object value (no delegate- or property-based Creator)
 at [Source: (byte[])"{"@class":"io.seata.rm.datasource.undo.BranchUndoLog","xid":"192.168.1.5:8091:298880381343518720","branchId":298880382744416257,"sqlUndoLogs":["java.util.ArrayList",[{"@class":"io.seata.rm.datasource.undo.SQLUndoLog","sqlType":"UPDATE","tableName":"stock_tbl","beforeImage":{"@class":"io.seata.rm.datasource.sql.struct.TableRecords","tableName":"stock_tbl","rows":["java.util.ArrayList",[{"@class":"io.seata.rm.datasource.sql.struct.Row","fields":["java.util.ArrayList",[{"@class":"io.seata.rm.dataso"[truncated 12232 bytes]; line: 1, column: 3987] (through reference chain: io.seata.rm.datasource.undo.BranchUndoLog["sqlUndoLogs"]->java.util.ArrayList[1]->io.seata.rm.datasource.undo.SQLUndoLog["afterImage"]->io.seata.rm.datasource.sql.struct.TableRecords["rows"]->java.util.ArrayList[0]->io.seata.rm.datasource.sql.struct.Row["fields"]->java.util.ArrayList[6]->io.seata.rm.datasource.sql.struct.Field["value"])

com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `java.time.LocalDateTime` (no Creators, like default constructor, exist): cannot deserialize from Object value (no delegate- or property-based Creator)
 at [Source: (byte[])"{"@class":"io.seata.rm.datasource.undo.BranchUndoLog","xid":"192.168.1.5:8091:298880381343518720","branchId":298880382744416257,"sqlUndoLogs":["java.util.ArrayList",[{"@class":"io.seata.rm.datasource.undo.SQLUndoLog","sqlType":"UPDATE","tableName":"stock_tbl","beforeImage":{"@class":"io.seata.rm.datasource.sql.struct.TableRecords","tableName":"stock_tbl","rows":["java.util.ArrayList",[{"@class":"io.seata.rm.datasource.sql.struct.Row","fields":["java.util.ArrayList",[{"@class":"io.seata.rm.dataso"[truncated 12232 bytes]; line: 1, column: 3987] (through reference chain: io.seata.rm.datasource.undo.BranchUndoLog["sqlUndoLogs"]->java.util.ArrayList[1]->io.seata.rm.datasource.undo.SQLUndoLog["afterImage"]->io.seata.rm.datasource.sql.struct.TableRecords["rows"]->java.util.ArrayList[0]->io.seata.rm.datasource.sql.struct.Row["fields"]->java.util.ArrayList[6]->io.seata.rm.datasource.sql.struct.Field["value"])
    at com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:67) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.DeserializationContext.reportBadDefinition(DeserializationContext.java:1615) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.DatabindContext.reportBadDefinition(DatabindContext.java:400) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1077) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromObjectUsingNonDefault(BeanDeserializerBase.java:1332) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:331) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:199) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:166) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsPropertyTypeDeserializer._deserializeTypedForId(AsPropertyTypeDeserializer.java:132) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsPropertyTypeDeserializer.deserializeTypedFromObject(AsPropertyTypeDeserializer.java:99) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsPropertyTypeDeserializer.deserializeTypedFromAny(AsPropertyTypeDeserializer.java:195) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.std.UntypedObjectDeserializer$Vanilla.deserializeWithType(UntypedObjectDeserializer.java:710) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:138) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:293) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:194) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:166) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsPropertyTypeDeserializer._deserializeTypedForId(AsPropertyTypeDeserializer.java:132) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsPropertyTypeDeserializer.deserializeTypedFromObject(AsPropertyTypeDeserializer.java:99) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeWithType(BeanDeserializerBase.java:1209) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:292) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:249) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:26) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsArrayTypeDeserializer._deserialize(AsArrayTypeDeserializer.java:120) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsArrayTypeDeserializer.deserializeTypedFromArray(AsArrayTypeDeserializer.java:53) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserializeWithType(CollectionDeserializer.java:318) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:138) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:293) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:194) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:166) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsPropertyTypeDeserializer._deserializeTypedForId(AsPropertyTypeDeserializer.java:132) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsPropertyTypeDeserializer.deserializeTypedFromObject(AsPropertyTypeDeserializer.java:99) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeWithType(BeanDeserializerBase.java:1209) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:292) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:249) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:26) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsArrayTypeDeserializer._deserialize(AsArrayTypeDeserializer.java:120) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsArrayTypeDeserializer.deserializeTypedFromArray(AsArrayTypeDeserializer.java:53) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserializeWithType(CollectionDeserializer.java:318) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:138) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:293) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:194) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:166) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsPropertyTypeDeserializer._deserializeTypedForId(AsPropertyTypeDeserializer.java:132) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsPropertyTypeDeserializer.deserializeTypedFromObject(AsPropertyTypeDeserializer.java:99) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeWithType(BeanDeserializerBase.java:1209) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:138) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:293) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:194) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:166) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsPropertyTypeDeserializer._deserializeTypedForId(AsPropertyTypeDeserializer.java:132) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsPropertyTypeDeserializer.deserializeTypedFromObject(AsPropertyTypeDeserializer.java:99) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeWithType(BeanDeserializerBase.java:1209) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:292) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:249) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:26) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsArrayTypeDeserializer._deserialize(AsArrayTypeDeserializer.java:120) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsArrayTypeDeserializer.deserializeTypedFromArray(AsArrayTypeDeserializer.java:53) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserializeWithType(CollectionDeserializer.java:318) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:138) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:293) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:194) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:166) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsPropertyTypeDeserializer._deserializeTypedForId(AsPropertyTypeDeserializer.java:132) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.jsontype.impl.AsPropertyTypeDeserializer.deserializeTypedFromObject(AsPropertyTypeDeserializer.java:99) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeWithType(BeanDeserializerBase.java:1209) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.deser.impl.TypeWrappedDeserializer.deserialize(TypeWrappedDeserializer.java:68) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4526) ~[jackson-databind-2.11.4.jar:2.11.4]
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3529) ~[jackson-databind-2.11.4.jar:2.11.4]
    at io.seata.rm.datasource.undo.parser.JacksonUndoLogParser.decode(JacksonUndoLogParser.java:139) ~[seata-all-1.3.0.jar:1.3.0]
    at io.seata.rm.datasource.undo.AbstractUndoLogManager.undo(AbstractUndoLogManager.java:276) [seata-all-1.3.0.jar:1.3.0]
    at io.seata.rm.datasource.DataSourceManager.branchRollback(DataSourceManager.java:178) [seata-all-1.3.0.jar:1.3.0]
    at io.seata.rm.AbstractRMHandler.doBranchRollback(AbstractRMHandler.java:125) [seata-all-1.3.0.jar:1.3.0]
    at io.seata.rm.AbstractRMHandler$2.execute(AbstractRMHandler.java:67) [seata-all-1.3.0.jar:1.3.0]
    at io.seata.rm.AbstractRMHandler$2.execute(AbstractRMHandler.java:63) [seata-all-1.3.0.jar:1.3.0]
    at io.seata.core.exception.AbstractExceptionHandler.exceptionHandleTemplate(AbstractExceptionHandler.java:116) [seata-all-1.3.0.jar:1.3.0]
    at io.seata.rm.AbstractRMHandler.handle(AbstractRMHandler.java:63) [seata-all-1.3.0.jar:1.3.0]
    at io.seata.rm.DefaultRMHandler.handle(DefaultRMHandler.java:63) [seata-all-1.3.0.jar:1.3.0]
    at io.seata.core.protocol.transaction.BranchRollbackRequest.handle(BranchRollbackRequest.java:35) [seata-all-1.3.0.jar:1.3.0]
    at io.seata.rm.AbstractRMHandler.onRequest(AbstractRMHandler.java:150) [seata-all-1.3.0.jar:1.3.0]
    at io.seata.core.rpc.processor.client.RmBranchRollbackProcessor.handleBranchRollback(RmBranchRollbackProcessor.java:63) [seata-all-1.3.0.jar:1.3.0]
    at io.seata.core.rpc.processor.client.RmBranchRollbackProcessor.process(RmBranchRollbackProcessor.java:58) [seata-all-1.3.0.jar:1.3.0]
    at io.seata.core.rpc.netty.AbstractNettyRemoting.lambda$processMessage$2(AbstractNettyRemoting.java:265) [seata-all-1.3.0.jar:1.3.0]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[na:1.8.0_275]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[na:1.8.0_275]
    at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) ~[netty-all-4.1.58.Final.jar:4.1.58.Final]
    at java.lang.Thread.run(Thread.java:748) ~[na:1.8.0_275]

二、原因分析

全局事务进行回滚时，会去查询undo_log 表中的回滚信息，回滚信息中记录了当前数据操作前后的镜像。

Seata 默认采用的序列化方式是 jackson，报错信息显示jackson 反序列化失败，我们定位到JacksonUndoLogParser类的decode()方法：

在数据库中，undio_log的时间字段 log_created和log_modified设置的是datetime 类型；

Seata 会自己去查询数据库字段的属性、值并缓存，在插入回滚信息时，将数据库的datetime 被解析为java.time.LocalDateTime。而Seata 在使用Jackson 序列化器时，没有对java.time.LocalDateTime类型序列化进行配置，导致报错。

三、解决方案

方案1、降低mysql-connector-java版本

调整mysql-connector-java版本 <= 8.0.22；

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.22</version>
</dependency>

在该版本下，数据库的datetime 被解析为java.sql.Timestamp，因此也就不存在java.time.LocalDateTime无法反序列化的问题了。

这种方案最简单、快速，推荐；

方案2、更换Seata的undo_log序列化方式

seata支持以下几种序列化方式：

• FastjsonUndoLogParser：Fastjson序列化工具
• FstUndoLogParser：Fst序列化工具（seata 1.4.x版本开始支持）
• JacksonUndoLogParser：Jackson序列化工具
• KryoUndoLogParser：Kryo序列化工具
• ProtostuffUndoLogParser：Protostuff序列化工具

有些序列化方式是不行的，实测结果如下：

• 仅有Protostuff、Kryo、Fst三种序列化方式是可行的；
• Fastjson 和 Jackson均不支持；

此外，seata 1.5.x版本修复了 FastjsonUndoLogParser 中 LocalDataTime 类型无法回滚的问题，也就是说seata 1.5.x版本Fastjson序列化方式也是可行的。

1）Seata undo配置类

UndoProperties中包含四个配置项：

• dataValidatioin：表示二阶段回滚镜像数据时是否进行校验，默认true开启；
• logSerialization：undo序列化方法，默认是jackson；
• logTable：undo表名，默认为undo_log
• onlyCareUpdateColumns：是否只检验SQL更新的字段，默认true开启；

相关常量：

public static final String SEATA_PREFIX = "seata";
public static final String CLIENT_PREFIX = SEATA_PREFIX + ".client";
public static final String UNDO_PREFIX = CLIENT_PREFIX + ".undo";

public static final boolean DEFAULT_TRANSACTION_UNDO_DATA_VALIDATION = true;
// 默认采用jsckson序列化协议
public static final String DEFAULT_TRANSACTION_UNDO_LOG_SERIALIZATION = "jackson";
public static final String DEFAULT_TRANSACTION_UNDO_LOG_TABLE = "undo_log";
public static final boolean DEFAULT_ONLY_CARE_UPDATE_COLUMNS = true;

2）自定义Seata undo_log序列化

修改log-serialization配置即可，默认使用的是jackson；如果需要修改为其他的，则需要在pom.xml中引入相关的序列化包依赖；一般不建议修改序列化方式，因为jackson是Sring Boot已集成的，无需再添加第三方包。

以protostuff序列化为例；

1> application.yml文件：

seata:
  client:
    undo:
      # 指定undo的序列化协议为protostuff
      log-serialization: protostuff

如果seata使用的是file配置方式，也可以选择直接在file.conf中修改：

client {
  undo {
    dataValidation = true
    logSerialization = "protostuff"
    logTable = "undo_log"
  }
}

2> pom.xml中引入protostuff相关依赖包：

<dependency>
    <groupId>io.protostuff</groupId>
    <artifactId>protostuff-runtime</artifactId>
    <version>1.8.0</version>
</dependency>
<dependency>
    <groupId>io.protostuff</groupId>
    <artifactId>protostuff-core</artifactId>
    <version>1.8.0</version>
</dependency>

方案3、将数据库字段类型从datetime修改为timestamp

这种方式不推荐，尤其是对于正常业务表，如果业务已经上线，再修改数据类型就很难搞。

方案4、使Jackson可以解析java.time.LocalDateTime类型

从seata 1.4.2版本开始 ；JacksonUndoLogParser源码中增加了对LocalDateTime类的序列化和反序列化处理；

从代码逻辑来看，我们需要一个实现JacksonSerializer的类，其中负责处理LocalDateTime类型，具体操作步骤如下：

1> 自定义支持可以解析java.time.OffsetDateTime类型的解析类；例如：

public class JsonDateTimeSerializer implements JacksonSerializer<LocalDateTime> {
 
    private static final DateTimeFormatter DATETIME_FORMAT = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
 
    @Override
    public Class<LocalDateTime> type() {
        return LocalDateTime.class;
    }
 
    @Override
    public JsonSerializer<LocalDateTime> ser() {
        return new LocalDateTimeSerializer(DATETIME_FORMAT);
    }
 
    @Override
    public JsonDeserializer<? extends LocalDateTime> deser() {
        return new LocalDateTimeDeserializer(DATETIME_FORMAT);
    }
}

2>在 META-INF/services 目录中定义名称为io.seata.rm.datasource.undo.UndoLogParser的文件，内容为JacksonSerializer实现类的全路径名；