前言

• springboot 2.1.1.RELEASE

源码

@Repository
public class TestDao {
	
	@Autowired
	private SqlSessionTemplate sqlSessionTemplate;
	
	public void printSysConfig() {
		String sql = "select * from sys_config";
		try (
			Connection conn = this.sqlSessionTemplate.getConnection();
			PreparedStatement ps = conn.prepareStatement(sql);
		) {
			ResultSet rs = ps.executeQuery();
			int cols = rs.getMetaData().getColumnCount();
			while (rs.next()) {
				for (int i=1;i<=cols;i++) {
					System.out.print(rs.getString(i));
					System.out.print(",");
				}
				System.out.println();
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

遇到错误 java.sql.SQLException: Connection is closed

java.sql.SQLException: Connection is closed
	at com.zaxxer.hikari.pool.ProxyConnection$ClosedConnection.lambda$getClosedConnection$0(ProxyConnection.java:515)
	at com.sun.proxy.$Proxy50.prepareStatement(Unknown Source)
	at com.zaxxer.hikari.pool.ProxyConnection.prepareStatement(ProxyConnection.java:337)
	at com.zaxxer.hikari.pool.HikariProxyConnection.prepareStatement(HikariProxyConnection.java)
	at com.ymyun.samples.TestDao.printSysConfig(TestDao.java:40)
	at com.ymyun.samples.TestDao$$FastClassBySpringCGLIB$$20d8ee9.invoke(<generated>)
	at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218)
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:771)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:749)
	at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
	at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:749)
	at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:691)
	at com.ymyun.samples.TestDao$$EnhancerBySpringCGLIB$$1cf3f5d2.printSysConfig(<generated>)
	at com.ymyun.samples.YmyunSamplesApplication.lambda$0(YmyunSamplesApplication.java:45)
	at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:784)
	at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:768)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:322)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215)
	at com._3jcf.ymyun.samples.YmyunSamplesApplication.main(YmyunSamplesApplication.java:38)

错误原因

参考
https://www.cnblogs.com/Zhongzz/p/9407639.html

解决办法

使用下面的方法获取Connection：

SqlSessionTemplate st = (SqlSessionTemplate) getSqlSession();
 
Connection connection = SqlSessionUtils.getSqlSession(
                st.getSqlSessionFactory(), st.getExecutorType(),
                st.getPersistenceExceptionTranslator()).getConnection();

修改后的源码

@Repository
public class TestDao {
	@Autowired
	private SqlSessionTemplate sqlSessionTemplate;

	public void printSysConfig() {
		String sql = "select * from sys_config";
		try (
			Connection conn = this.getConnection();
			PreparedStatement ps = conn.prepareStatement(sql);
		) {
			ResultSet rs = ps.executeQuery();
			int cols = rs.getMetaData().getColumnCount();
			while (rs.next()) {
				for (int i=1;i<=cols;i++) {
					System.out.print(rs.getString(i));
					System.out.print(",");
				}
				System.out.println();
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	private Connection getConnection() {
		SqlSessionTemplate st = this.sqlSessionTemplate;
		Connection connection = SqlSessionUtils.getSqlSession(
                st.getSqlSessionFactory(), st.getExecutorType(),
                st.getPersistenceExceptionTranslator()).getConnection();
		return connection;
	}
}