开启事务过程中，如果远程调用查询当前已经开启但没有提交的事务，就会查不到数据。
示例代码
java
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
import java.util.Objects;
@Slf4j
@RestController
@RequestMapping("simple")
@RequiredArgsConstructor
public class SimpleController {
private final SimpleObjectMapper simpleObjectMapper;
private final RestTemplate restTemplate;
/**
* 开启事务过程中，如果远程调用查询当前已经开启但没有提交的事务，就会查不到数据。
*/
@GetMapping("insert")
@Transactional(rollbackFor = Exception.class)//1.开启事务
public void insert() {
SimpleObject simpleObject = new SimpleObject();
simpleObject.setId(2);
simpleObject.setName("name" + System.currentTimeMillis());
simpleObjectMapper.insert(simpleObject);//2.因为开启了事务，所以这里的 insert 并没有 commit，导致下面远程调用查询数据是空的。
SimpleObject simpleObject1 = restTemplate.getForEntity("http://localhost:8080/simple/2", SimpleObject.class, simpleObject.getId()).getBody();
log.info("simpleObject1 （这里会输出null）：{}",simpleObject1);//3.这里会输出null，因为事务没有提交，数据库不会新增数据
if (Objects.isNull(simpleObject1)) {
throw new RuntimeException("simpleObject1 is null");
}
}
/**
* 被远程调用的查询方法
*/
@GetMapping("{id}")
public SimpleObject selectById(@PathVariable Integer id) {
return simpleObjectMapper.selectById(id);
}
}抛出异常
shell
2024-05-23 22:49:44.033 INFO 8668 --- [nio-8080-exec-1] MyBatisSqlParsingPlugin : Execute SQL:
INSERT INTO simple_object ( id,name ) VALUES ( 2,'name1716475783993' )
2024-05-23 22:49:44.119 INFO 8668 --- [nio-8080-exec-2] MyBatisSqlParsingPlugin : Execute SQL:
SELECT id,name FROM simple_object WHERE id=2
2024-05-23 22:49:44.149 INFO 8668 --- [nio-8080-exec-1] SimpleController : simpleObject1 （这里会输出null）：null
2024-05-23 22:49:44.161 ERROR 8668 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet] :
java.lang.RuntimeException: simpleObject1 is null解决办法
1、去掉@Transactional注解（显然不可能，除非不影响正常的业务）
2、手动控制事务，但是有些情况下可能不适用，不适用的情况可以使用分布式事务，如：seata等（推荐）
手动控制事务
示例代码
java
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.TransactionDefinition;
import org.springframework.transaction.TransactionStatus;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
import java.util.Objects;
@Slf4j
@RestController
@RequestMapping("simple")
@RequiredArgsConstructor
public class SimpleController {
private final SimpleObjectMapper simpleObjectMapper;
private final RestTemplate restTemplate;
private final PlatformTransactionManager platformTransactionManager;//事务管理器
private final TransactionDefinition transactionDefinition;// 事务的一些基础信息，如超时时间、隔离级别、传播属性等
/**
* 使用手动事务，远程调用可以查询到数据。
*/
@GetMapping("insert2")
public void insert2() {
//手动事务不能加@Transactional注解，否则优先使用@Transactional注解的事务
TransactionStatus transaction = platformTransactionManager.getTransaction(transactionDefinition);//1、手动获取事务
SimpleObject simpleObject = new SimpleObject();
try {
simpleObject.setId(2);
simpleObject.setName("name" + System.currentTimeMillis());
simpleObjectMapper.insert(simpleObject);
platformTransactionManager.commit(transaction);//2.手动提交事务
} catch (Exception e) {
platformTransactionManager.rollback(transaction);//4.发生异常手动回滚事务
log.error("insert2异常：", e);
throw new RuntimeException( "insert2异常：" + e.getMessage());
}
SimpleObject simpleObject1 = restTemplate.getForEntity("http://localhost:8080/simple/2", SimpleObject.class, simpleObject.getId()).getBody();
log.info("simpleObject1 （这里会输出simpleObject1）：{}",simpleObject1);//3.这里会输出id = 2的 SimpleObject 对象，因为事务提交，数据库会新增数据
if (Objects.isNull(simpleObject1)) {
throw new RuntimeException("simpleObject1 is null");
}
}
/**
* 被远程调用的查询方法
*/
@GetMapping("{id}")
public SimpleObject selectById(@PathVariable Integer id) {
return simpleObjectMapper.selectById(id);
}
}不抛出异常，可以正常获取数据
shell
2024-05-23 23:02:00.506 INFO 10608 --- [nio-8080-exec-1] c.f.m.plugin.MyBatisSqlParsingPlugin : Execute SQL:
INSERT INTO simple_object ( id,
name ) VALUES ( 2,
'name1716476520466' )
2024-05-23 23:02:00.592 INFO 10608 --- [nio-8080-exec-2] c.f.m.plugin.MyBatisSqlParsingPlugin : Execute SQL:
SELECT id,name FROM simple_object WHERE id=2
2024-05-23 23:02:00.641 INFO 10608 --- [nio-8080-exec-1] c.f.m.controller.SimpleController : simpleObject1 （这里会输出simpleObject1）：SimpleObject(id=2, name=name1716476520466)不使用事务（不推荐）
示例代码
java
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.TransactionDefinition;
import org.springframework.transaction.TransactionStatus;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
import java.util.Objects;
@Slf4j
@RestController
@RequestMapping("simple")
@RequiredArgsConstructor
public class SimpleController {
private final SimpleObjectMapper simpleObjectMapper;
private final RestTemplate restTemplate;
/**
* 不使用事务，远程调用可以查询到数据。（不推荐）
*/
@GetMapping("insert3")
public void insert3() {
SimpleObject simpleObject = new SimpleObject();
simpleObject.setId(2);
simpleObject.setName("name" + System.currentTimeMillis());
simpleObjectMapper.insert(simpleObject);//1、因为没有事务，所以这里会新增数据到数据库
SimpleObject simpleObject1 = restTemplate.getForEntity("http://localhost:8080/simple/2", SimpleObject.class, simpleObject.getId()).getBody();
log.info("simpleObject1 （这里会输出simpleObject1）：{}",simpleObject1);//2.这里会输出id = 2的 SimpleObject 对象，因为事务提交，数据库会新增数据
if (Objects.isNull(simpleObject1)) {
throw new RuntimeException("simpleObject1 is null");
}
}
/**
* 被远程调用的查询方法
*/
@GetMapping("{id}")
public SimpleObject selectById(@PathVariable Integer id) {
return simpleObjectMapper.selectById(id);
}
}不抛出异常，可以正常获取数据
shell
2024-05-23 23:04:31.889 INFO 10608 --- [nio-8080-exec-6] c.f.m.plugin.MyBatisSqlParsingPlugin : Execute SQL:
INSERT INTO simple_object ( id,
name ) VALUES ( 2,
'name1716476671888' )
2024-05-23 23:04:31.895 INFO 10608 --- [nio-8080-exec-7] c.f.m.plugin.MyBatisSqlParsingPlugin : Execute SQL:
SELECT id,name FROM simple_object WHERE id=2
2024-05-23 23:04:31.897 INFO 10608 --- [nio-8080-exec-6] c.f.m.controller.SimpleController : simpleObject1 （这里会输出simpleObject1）：SimpleObject(id=2, name=name1716476671888)