初始化 c3p0 池期间获取尝试失败

Question

我是 J2EE 技术的新手，正在尝试使用 JSF、Spring 和 Hibernate 创建一个基本的 Web 应用程序。我也使用 PostgreSQL。在服务器启动过程中，我遇到了这个异常：

WARNING: com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@173b4cf -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception: 
java.lang.NullPointerException
at sun.jdbc.odbc.JdbcOdbcDriver.getProtocol(Unknown Source)
at sun.jdbc.odbc.JdbcOdbcDriver.knownURL(Unknown Source)
at sun.jdbc.odbc.JdbcOdbcDriver.acceptsURL(Unknown Source)
at java.sql.DriverManager.getDriver(Unknown Source)
at com.mchange.v2.c3p0.DriverManagerDataSource.driver(DriverManagerDataSource.java:240)
at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:131)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:156)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:145)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPoolPooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:200)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1086)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1073)
at com.mchange.v2.resourcepool.BasicResourcePool.access0(BasicResourcePool.java:44)
at com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1810)
at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:648)

Dec 09, 2015 11:13:21 AM com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask run
WARNING: com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@173b4cf -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception: 
java.lang.NullPointerException
at sun.jdbc.odbc.JdbcOdbcDriver.getProtocol(Unknown Source)
at sun.jdbc.odbc.JdbcOdbcDriver.knownURL(Unknown Source)
at sun.jdbc.odbc.JdbcOdbcDriver.acceptsURL(Unknown Source)
at java.sql.DriverManager.getDriver(Unknown Source)
at com.mchange.v2.c3p0.DriverManagerDataSource.driver(DriverManagerDataSource.java:240)
at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:131)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:156)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:145)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPoolPooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:200)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1086)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1073)
at com.mchange.v2.resourcepool.BasicResourcePool.access0(BasicResourcePool.java:44)
at com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1810)
at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:648)

Dec 09, 2015 11:13:21 AM com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask run
WARNING: com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask@5e53d -- Acquisition Attempt Failed!!! Clearing pending acquires. While trying to acquire a needed new resource, we failed to succeed more than the maximum number of allowed acquisition attempts (30). Last acquisition attempt exception: 
java.lang.NullPointerException
at sun.jdbc.odbc.JdbcOdbcDriver.getProtocol(Unknown Source)
at sun.jdbc.odbc.JdbcOdbcDriver.knownURL(Unknown Source)
at sun.jdbc.odbc.JdbcOdbcDriver.acceptsURL(Unknown Source)
at java.sql.DriverManager.getDriver(Unknown Source)
at com.mchange.v2.c3p0.DriverManagerDataSource.driver(DriverManagerDataSource.java:240)
at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:131)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:156)
at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:145)
at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPoolPooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:200)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1086)
at com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1073)
at com.mchange.v2.resourcepool.BasicResourcePool.access0(BasicResourcePool.java:44)
at com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1810)
at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:648)

我在下面给出了我的配置文件和相关 class：

申请-context.xml:

<?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:context="http://www.springframework.org/schema/context"
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
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context.xsd">

<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
    <property name="driverClassName" value="org.postgresql.Driver" />
    <property name="url" value="jdbc:postgresql://localhost:5432/SomeDB" />
    <property name="username" value="postgres" />
    <property name="password" value="1234" />
</bean>

<bean id="sessionFactory" class="org.springframework.orm.hibernate5.LocalSessionFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="packagesToScan" value="tr.mypackage" />
    <property name="hibernateProperties">
        <props>
            <prop key="hibernate.dialect">org.hibernate.dialect.PostgreSQLDialect</prop>
            <prop key="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</prop>
            <prop key="hibernate.c3p0.acquire_increment">1</prop>
        </props>
    </property>
</bean>

<bean id="transactionManager" class="org.springframework.orm.hibernate5.HibernateTransactionManager">
    <property name="sessionFactory" ref="sessionFactory" />
</bean>

<tx:annotation-driven transaction-manager="transactionManager" />
<context:annotation-config />
<context:component-scan base-package="tr.mypackage" />

</beans>

web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
id="WebApp_ID" version="3.1">
<display-name>Some Display Name</display-name>

<!-- JSF -->
<servlet>
    <servlet-name>Faces Servlet</servlet-name>
    <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
</servlet>

<servlet-mapping>
    <servlet-name>Faces Servlet</servlet-name>
    <url-pattern>*.xhtml</url-pattern>
</servlet-mapping>

<!-- SPRING -->
<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>/WEB-INF/application-context.xml</param-value>
</context-param>

<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

<listener>
    <listener-class>org.springframework.web.context.request.RequestContextListener</listener-class>
</listener>

<!-- OTHER -->
<welcome-file-list>
    <welcome-file>index.xhtml</welcome-file>
</welcome-file-list>
</web-app>

Person.java

package tr.mypackage;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

import com.sun.istack.internal.NotNull;

@Entity
@Table(name="person_t")
public class Person {
    @Id
    @NotNull
    @GeneratedValue
    private int id;

    @Column
    private String firstName;

    public Person(){

    }

    public Person(int id, String firstName) {
        super();
        this.id = id;
        this.firstName = firstName;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

}

那么，你知道我的错误在哪里吗？

Answer 1

问题的直接原因是您实际上没有向使用这些设置休眠构建的 c3p0 数据源提供任何连接信息。

<prop key="hibernate.connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</prop>
<prop key="hibernate.c3p0.acquire_increment">1</prop>

参见 Spring docs：您在 Spring 中配置的数据源与 hibernate 的 SessionFactory 可能在内部构建的数据源不同。您已经提供了足够的配置来让休眠构建数据源，但是您还没有提供正确配置它所必需的 hibernate.connection.* 参数。

最简单的做法是删除您在 Spring 中配置的数据源，并在休眠状态下完成 c3p0 数据源的配置。见 hibernate docs for the various Connection parameters you should supply that currently are missing. You can also set c3p0 configuration parameters as hibernate.c3p0.fooBarBlah (where fooBarBlah should obviously be replaced by real parameter names). [Note that for parameters like max_size and maxPoolSize with both a hibernate name and a c3p0 name, the hibernate name will override c3p0-name settings.]

或者，您可以去掉上面的两个休眠属性，并提供您自己在 Spring 中配置的数据源。如果您想要连接池，您可能不会将数据源设为 org.springframework.jdbc.datasource.DriverManagerDataSource。您可以直接在 Spring 中配置 com.mchange.v2.c3p0.ComboPooledDataSource，就像您配置 unpooled DriverManagerDataSource 一样。有关示例，请参阅 this article 中的 "Have Spring Manage the Pool" 部分。

Answer 2

如果您使用的是 eclipse 并且遇到此错误，那么您只需更改 mysql 连接器（在我的情况下它工作得很好）。

较新的版本正在使用 caching_sha2_password。

初始化 c3p0 池期间获取尝试失败

Acquisition attempt failed during the initializing c3p0 pool

postgresql

spring

hibernate

c3p0