最近在学习spring框架，但是在学到JdbcTemplate时连接数据库一直报错，百度谷歌各种查找都能没有解决问题，简直要癫狂，报错信息如下：

org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: Connections could not be acquired from the underlying database!

at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:80)

at org.springframework.jdbc.core.JdbcTemplate.execute(JdbcTemplate.java:390)

at org.springframework.jdbc.core.JdbcTemplate.update(JdbcTemplate.java:534)

at cn.itcast.a_jdbctemplate.Demo.fun1(Demo.java:38)

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:498)

at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)

at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)

at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)

at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)

at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)

at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)

at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)

at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)

at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:254)

at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:89)

at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)

at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)

at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)

at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)

at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)

at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)

at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)

at org.junit.runners.ParentRunner.run(ParentRunner.java:363)

at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:193)

at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)

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:678)

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: Connections could not be acquired from the underlying database!

at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106)

at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:529)

at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128)

at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:111)

at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:77)

... 32 more

Caused by: com.mchange.v2.resourcepool.CannotAcquireResourceException: A ResourcePool could not acquire a resource from its primary factory or source.

at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1319)

at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:557)

at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477)

at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525)

... 35 more

最后的原因是我使用的数据库是Mysql8,太新了，相对以前我使用的Mysql5需要在url参数上添加一些参数，(吐血。。。。。)，调了三天，期间换了IDE，MySQL等等，最后解决方法是把url换成这样：

jdbc:mysql:///spring?useSSL=false&serverTimezone=UTC&characterEncoding=utf8

重点是设置：useSSL=false

还有一点，最新的mysql驱动类应当是：com.mysql.cj.jdbc.Driver，以前的 com.mysql.cj.jdbc.Driver提示被废弃了。

最后完整的测试代码供君借鉴：

@Test

public void test05() throws Exception {

// 创建数据源

ComboPooledDataSource dataSource = new ComboPooledDataSource();

//设置连接相关参数

dataSource.setDriverClass("com.mysql.cj.jdbc.Driver");

dataSource.setJdbcUrl("jdbc:mysql:///spring?useSSL=false&serverTimezone=UTC&characterEncoding=utf8");

dataSource.setUser("root");

dataSource.setPassword("123456");

//创建模板对象

JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);

//测试相关代码是否执行

System.out.println("Hello");

String sql = "insert into jdbc_template values(null,'Nick') ";

jdbcTemplate.update(sql);

System.out.println("!!!!!!!!!!!OK!!!!!!!!!!!!!!!!");

}

数据库创建代码：

CREATE DATABASE spring;

USE spring;

CREATE TABLE jdbc_template(

id INT AUTO_INCREMENT PRIMARY KEY,

NAME VARCHAR(255) NOT NULL

);

INSERT INTO jdbc_template VALUES(NULL,'rose') ;

SELECT * FROM jdbc_template;