Java Batch(JSR352)中Batchlet执行JPA删除查询的事务异常问题

问题场景 #

现有一个Java Batch作业，可完成数据读取、处理及数据库存储操作，需新增一个删除数据的步骤。由于Chunk的Reader/Processor/Writer模式不适用该场景，采用Batchlet方案，但执行JPA删除查询时始终抛出javax.persistence.TransactionRequiredException: Executing an update/delete query异常。尝试过手动管理事务、切换JTA/非JTA持久化单元、自行创建EntityManager等方式，均未解决问题。相关代码如下：

package ...;

import javax.batch.api.BatchProperty;
import javax.inject.Inject;
import javax.inject.Named;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

@Named("CleanerBatchlet")
public class CleanerBatchlet extends AbstractBatchlet {
    public static final Logger log = LogManager.getLogger(CleanerBatchlet.class);

    @PersistenceContext(unitName = "...")
    private EntityManager entityManager;  

    @Inject
    @BatchProperty(name = "technologyIds")
    private String technologyIds;
    
    private void clearQueue(long technologyId) {
        //EntityManager entityManager = ...getEntityManager();
        
        //entityManager.getTransaction().begin();
        Query q = entityManager.createQuery("delete from Record r where r.technologyId=:technologyId");
        q.setParameter("technologyId", technologyId);
        int count = q.executeUpdate();
        //entityManager.getTransaction().commit();
        log.debug("Deleted {} entries from queue {}", count, technologyId);
        
        //entityManager.close();
    }
    
    @Override
    public String doProcess() throws Exception {
        log.debug("doProcess()");
        out.println("technologyIds=" + technologyIds);
        log.info("technologyIds=" + technologyIds);
        try {
            String[] parts = technologyIds.split(",");
            for (String part: parts) {
                long technologyId = Long.parseLong(part);
                clearQueue(technologyId);
            }
        } catch (NullPointerException | NumberFormatException e) {
            throw new IllegalStateException("technologyIds must be set to a string of comma-separated numbers.", e);
        }
        return "COMPLETED";
    }

}

解决方案 #

1. 为Batchlet添加事务上下文 #

Java Batch默认不会为Batchlet自动开启事务，需手动启用容器管理事务或手动控制事务：

方式一：容器管理事务（推荐）

给doProcess方法添加@Transactional注解（Jakarta EE环境用jakarta.transaction.Transactional，旧版Java EE用javax.transaction.Transactional），由容器自动管理事务的开启、提交与回滚：

import jakarta.transaction.Transactional;

// ...

@Override
@Transactional
public String doProcess() throws Exception {
    // 原有逻辑保持不变
}

方式二：手动管理JTA事务

注入UserTransaction手动控制事务生命周期：

import jakarta.transaction.UserTransaction;
import javax.persistence.Query;

// ...

@Inject
private UserTransaction userTransaction;

private void clearQueue(long technologyId) throws Exception {
    userTransaction.begin();
    try {
        Query q = entityManager.createQuery("delete from Record r where r.technologyId=:technologyId");
        q.setParameter("technologyId", technologyId);
        int count = q.executeUpdate();
        log.debug("Deleted {} entries from queue {}", count, technologyId);
        userTransaction.commit();
    } catch (Exception e) {
        userTransaction.rollback();
        throw e;
    }
}

2. 检查持久化单元配置 #

确保persistence.xml中持久化单元使用JTA事务类型，容器环境下优先使用JTA：

<persistence-unit name="..." transaction-type="JTA">
    <!-- 数据源、实体映射等其他配置 -->
</persistence-unit>

若使用RESOURCE_LOCAL类型，需手动创建EntityManagerFactory并管理事务，但这种方式在容器环境下易出错，不推荐。

3. 优先使用容器注入的EntityManager #

容器注入的EntityManager会自动关联JTA事务，自行创建的EntityManager（如通过EntityManagerFactory.createEntityManager()）需手动管理事务，容易引发异常，建议优先依赖容器注入实例。

内容的提问来源于stack exchange，提问作者queeg