完整代码

Question

我正在尝试将一些现有的Java 6代码升级到Java 7，并且在处理由spring事务管理的JDBC连接时，我遇到了新的try-with-resources语法问题。数据库连接由Oracle UCP管理，并使用Spring提供的DataSourceUtils类进行检索。但是，为了创建这个问题的简单示例，我使用的是HSQLDB 2.3.2和Apache commons-dbcp 2.0.1。两种设置都会出现同样的问题。当Spring TransactionInterceptor提交事务时发生异常：

org.springframework.transaction.TransactionSystemException: Could not commit JDBC transaction; nested exception is java.sql.SQLException: Connection is null.
    at org.springframework.jdbc.datasource.DataSourceTransactionManager.doCommit(DataSourceTransactionManager.java:272)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:757)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:726)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:496)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:276)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:95)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:653)
    at com.creaseol.dao.SampleDao$$EnhancerBySpringCGLIB$$45ec8efa.putWithTryWithResources(<generated>)
    at com.creaseol.TestTryCatch.testWithResources(TestTryCatch.java:69)
    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:483)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:72)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:81)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:216)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:82)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:60)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:67)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:162)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: java.sql.SQLException: Connection is null.
    at org.apache.commons.dbcp2.DelegatingConnection.checkOpen(DelegatingConnection.java:608)
    at org.apache.commons.dbcp2.DelegatingConnection.commit(DelegatingConnection.java:362)
    at org.springframework.jdbc.datasource.DataSourceTransactionManager.doCommit(DataSourceTransactionManager.java:269)
    ... 40 more

我创建了一个简单的Maven项目来显示问题。所需的四个文件如下。我有一个DAO，它有以下两种用@Transactional注释的方法：

protected Connection getConnection() {
    return DataSourceUtils.getConnection(m_ds);
}

@Transactional
public void putWithNormalTryCatch(int id) {
    Connection conn = null;
    CallableStatement statement = null;
    try {
        conn = getConnection();
        statement = conn.prepareCall(String.format("INSERT INTO test VALUES (%s)", id));
        statement.execute();
    }
    catch (SQLException sql) {
        throw new RuntimeException("failed during insert",sql);
    }
    finally {
        if (statement != null){
            try {
                statement.close();
            }
            catch (SQLException sqle) {
                System.err.println("Failed to close statement after execution. "+ sqle.getMessage());
            }
        }
        if (conn != null) {
            DataSourceUtils.releaseConnection(conn, m_ds);
        }
    }
}

@Transactional
public void putWithTryWithResources(int id) {
    try (Connection conn = getConnection();
         CallableStatement statement = conn.prepareCall(String.format("INSERT INTO test VALUES (%s)", id)))
    {
        statement.execute();
    }
    catch (SQLException sql) {
        throw new RuntimeException("failed during insert",sql);
    }
}

第一个方法putWithNormalTryCatch使用旧样式try catch块，putWithTryWithResources使用Java 7 try-with-resources。请注意，使用DataSourceUtils.getConnection检索连接，并使用DataSourceUtils.releaseConnection发布。

我认为问题在于try-with-resources实际上是在连接上调用close，而不是将其释放到池中。您真正想要的是在连接呼叫close()上呼叫DataSourceUtils.releaseConnection。

我可以简单地将DataSource包装在TransactionAwareDataSourceProxy中，但根据文档，这不是必需的。有更好的方法吗？

完整代码

DAO

package com.creaseol.dao;

import java.sql.CallableStatement;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import javax.sql.DataSource;

import org.springframework.jdbc.datasource.DataSourceUtils;
import org.springframework.transaction.annotation.Transactional;

public class SampleDao {

    private final DataSource m_ds;

    public SampleDao(DataSource ds) {
        m_ds = ds;
    }

    protected Connection getConnection() {
        return DataSourceUtils.getConnection(m_ds);
    }

    @Transactional
    public void putWithNormalTryCatch(int id) {
        Connection conn = null;
        CallableStatement statement = null;
        try {
            conn = getConnection();
            statement = conn.prepareCall(String.format("INSERT INTO test VALUES (%s)", id));
            statement.execute();
        }
        catch (SQLException sql) {
            throw new RuntimeException("failed during insert",sql);
        }
        finally {
            if (statement != null){
                try {
                    statement.close();
                }
                catch (SQLException sqle) {
                    System.err.println("Failed to close statement after execution. "+ sqle.getMessage());
                }
            }
            if (conn != null) {
                DataSourceUtils.releaseConnection(conn, m_ds);
            }
        }
    }

    @Transactional
    public void putWithTryWithResources(int id) {
        try (Connection conn = getConnection();
             CallableStatement statement = conn.prepareCall(String.format("INSERT INTO test VALUES (%s)", id)))
        {
            statement.execute();
        }
        catch (SQLException sql) {
            throw new RuntimeException("failed during insert",sql);
        }
    }

    public List<Integer> getValues() {
        try (Connection conn = getConnection();
             CallableStatement statement = conn.prepareCall("SELECT id FROM test"))
        {
            statement.execute();
            try (ResultSet rs = statement.getResultSet()) {
                List<Integer> values = new ArrayList<Integer>();
                while(rs.next()){
                    values.add(rs.getInt(1));
                }
                return values;
            }
        }
        catch (SQLException sql) {
            throw new RuntimeException("failed during insert",sql);
        }
    }
}

Spring上下文

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="  
            http://www.springframework.org/schema/beans        
            http://www.springframework.org/schema/beans/spring-beans.xsd   
            http://www.springframework.org/schema/tx    
            http://www.springframework.org/schema/tx/spring-tx.xsd">

    <bean id="dataSource" class="org.apache.commons.dbcp2.BasicDataSource"
        destroy-method="close">
        <property name="driverClassName" value="org.hsqldb.jdbc.JDBCDriver" />
        <property name="url" value="jdbc:hsqldb:mem:testdb" />
    </bean>

    <bean id="sampleDao" class="com.creaseol.dao.SampleDao">
        <constructor-arg ref="dataSource"/>
    </bean> 

    <bean id="transactionManager"
        class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource" />
    </bean>
    <tx:annotation-driven transaction-manager="transactionManager" />
</beans>

的pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.creaseol</groupId>
    <artifactId>SpringDBJava7Test</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <properties>
        <spring.version>4.1.1.RELEASE</spring.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-dbcp2</artifactId>
            <version>2.0.1</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-tx</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <!-- TEST DEPENDENCIES -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>${spring.version}</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>${spring.version}</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
            <scope>test</scope>
        </dependency>
        <!-- our in-memory database provider -->
        <dependency>
            <groupId>org.hsqldb</groupId>
            <artifactId>hsqldb</artifactId>
            <version>2.3.2</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.7</source>
                    <target>1.7</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

测试类

package com.creaseol;

import static org.junit.Assert.assertEquals;

import java.sql.CallableStatement;
import java.sql.Connection;
import java.sql.SQLException;

import javax.sql.DataSource;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.datasource.DataSourceUtils;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

import com.creaseol.dao.SampleDao;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:test-context.xml")
public class TestTryCatch {

    @Autowired
    private DataSource dataSource;

    @Autowired
    protected SampleDao m_dao;

    protected Connection getConnection(){
        return DataSourceUtils.getConnection(dataSource);
    }

    @Before
    public void setup() throws SQLException{
        Connection conn = getConnection();
        CallableStatement statement = conn.prepareCall("CREATE TABLE test (id INTEGER)");
        statement.execute();
        statement.close();
        close(conn);
    }

    protected void close(Connection conn) {
        if (conn != null){
            DataSourceUtils.releaseConnection(conn, dataSource);
        }
    }

    @After
    public void tearDown() throws SQLException {
        Connection conn = getConnection();
        CallableStatement statement = conn.prepareCall("DROP TABLE test");
        statement.execute();
        statement.close();
        close(conn);
    }

    @Test
    public void testVanilla(){
        m_dao.putWithNormalTryCatch(42);
        assertEquals(1,m_dao.getValues().size());
        assertEquals(42,(int)m_dao.getValues().get(0));
    }

    @Test
    public void testWithResources(){
        m_dao.putWithTryWithResources(100);
        assertEquals(1,m_dao.getValues().size());
        assertEquals(100,(int)m_dao.getValues().get(0));
    }
}

Answer 1

如果您有一些资源想要与try-with-resources语句一起使用，但它不是AutoCloseable（例如，java.util.concurrent.locks.ReentrantLock您希望在其中解锁块的结尾），或者您不想关闭而是要执行某些其他操作，就像您想要释放回池中的数据库连接一样，您可以将其包装在一个调用任何内容的包装器中您想要执行的操作而不是close()。

public class ReleasableConnection implements AutoCloseable {
    private final Connection connection;
    private final DataSource dataSource;
    private boolean released;

    public ReleaseableConnection(Connection connection, DataSource dataSource) {
        this.connection = connection;
        this.dataSource = dataSource;
        released = false;
    }

    public Connection getConnection() {
        return connection;
    }

    @Override
    public void close() {
        if (!released) {
            DataSourceUtils.releaseConnection(connection, dataSource);
            released = true; // make it idempotent
        }
    }
}

然后您可以在try-with-resources块中使用它，如下所示：

try (ReleasableConnection rc = new ReleasableConnection(getConnection(), m_ds)) {
    Connection conn = rc.getConnection();
    // do something with the connection
    // it will be released automatically
}

使用spring事务的Java 7 try-with-resources会在提交时导致连接关闭

完整代码

DAO

Spring上下文

的pom.xml

测试类

1 个答案: