Java基于JNDI 实现读写分离的示例代码

目录

• 一、JNDI数据源配置
• 二、JNDI数据源使用
• 三、web.xml配置
• 四、spring-servlet.xml配置
• 五、spring-db.xml配置
• 六、log4j.properties配置
• 七、相关路由数据源切换逻辑代码
• 八、搭建过程中遇到的问题和解决方案

一、JNDI数据源配置

在Tomcat的conf目录下，context.xml在其中标签中添加如下JNDI配置：

<Resource name="dataSourceMaster" factory="org.apache.tomcat.jdbc.pool.DataSourceFactory"
 auth="Container" type="javax.sql.DataSource" maxActive="100" maxIdle="30" maxWaitMillis="30000"
 username="root" password="root" driverClassName="com.mysql.jdbc.Driver"  url="jdbc:mysql://localhost:3306/user_master?useUnicode=true&amp;characterEncoding=utf-8"/>
<Resource name="dataSourceSlave" factory="org.apache.tomcat.jdbc.pool.DataSourceFactory"
 auth="Container" type="javax.sql.DataSource" maxActive="100" maxIdle="30" maxWaitMillis="30000"
 username="root" password="root" driverClassName="com.mysql.jdbc.Driver"  url="jdbc:mysql://localhost:3306/user_slave?useUnicode=true&amp;characterEncoding=utf-8"/>

二、JNDI数据源使用

1、在普通web项目中

（1）在web.xml文件中添加如下配置（也可以不配置）：

<resource-ref>
 <res-ref-name>dataSourceMaster</res-ref-name>
 <res-type>javax.sql.DataSource</res-type>
 <res-auth>Container</res-auth>
</resource-ref>
<resource-ref>
 <res-ref-name>dataSourceSlave</res-ref-name>
 <res-type>javax.sql.DataSource</res-type>
 <res-auth>Container</res-auth>
</resource-ref>

三、web.xml配置

<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd" >
<web-app>
 <display-name>Archetype Created Web Application</display-name>
 <context-param>
  <param-name>log4jConfigLocation</param-name>
  <param-value>classpath:log4j.properties</param-value>
 </context-param>
 <context-param>
  <param-name>log4jRefreshInterval</param-name>
  <param-value>60000</param-value>
 </context-param>
 <filter>
  <filter-name>CharacterEncodingFilter</filter-name>
  <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
  <init-param>
   <param-name>encoding</param-name>
   <param-value>utf-8</param-value>
  </init-param>
  <init-param>
   <param-name>forceEncoding</param-name>
   <param-value>true</param-value>
  </init-param>
 </filter>
 <filter-mapping>
  <filter-name>CharacterEncodingFilter</filter-name>
  <servlet-name>xiyun</servlet-name>
 </filter-mapping>
 <servlet>
  <servlet-name>xiyun</servlet-name>
  <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
  <init-param>
   <param-name>contextConfigLocation</param-name>
   <param-value>        classpath:conf/spring/spring-servlet.xml      </param-value>
  </init-param>
  <load-on-startup>1</load-on-startup>
 </servlet>
 <servlet-mapping>
  <servlet-name>xiyun</servlet-name>
  <url-pattern>*.do</url-pattern>
 </servlet-mapping>
</web-app>

四、spring-servlet.xml配置

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

 <context:component-scan base-package="com.xiaoxi"/>    

 <mvc:annotation-driven/>    

 <import resource="classpath:conf/spring/spring-db.xml"/>    

 <bean id="viewResolver"          class="org.springframework.web.servlet.view.InternalResourceViewResolver">
  <property name="prefix" value="/WEB-INF/freemarker/"/>
  <property name="suffix" value=".ftl"/>
  </bean>
 </beans>

五、spring-db.xml配置

<?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:aop="http://www.springframework.org/schema/aop"       xmlns:context="http://www.springframework.org/schema/context"
 xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
 http://www.springframework.org/schema/context  http://www.springframework.org/schema/context/spring-context.xsd
 http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd" >    

 <!-- 主数据源配置 -->
 <bean id="dataSourceMaster" class="org.springframework.jndi.JndiObjectFactoryBean">
  <property name="jndiName" value="java:comp/env/dataSourceMaster"/>
 </bean>
 <!-- 从数据源配置 -->
 <bean id="dataSourceSlave" class="org.springframework.jndi.JndiObjectFactoryBean">
  <property name="jndiName" value="java:comp/env/dataSourceSlave"/>
 </bean>    

 <aop:aspectj-autoproxy proxy-target-class="true"/>    

    <context:annotation-config/>    

 <bean id="dynamicDataSource" class="com.xiaoxi.config.DynamicRoutingDataSource">
  <property name="targetDataSources">
   <map>
    <entry key="Master" value-ref="dataSourceMaster"/>
    <entry key="Slave" value-ref="dataSourceSlave"/>
   </map>
  </property>
  <property name="defaultTargetDataSource" value="dataSourceMaster"/>
 </bean>    

 <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
  <!-- 配置数据源 -->
  <property name="dataSource" ref="dynamicDataSource"/>
 </bean>    

 <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
  <!-- 映射数据源 -->
  <property name="dataSource" ref="dynamicDataSource"/>
  <!-- 映射mybatis核心配置文件 -->
  <property name="configLocation" value="classpath:conf/spring/mybatis-config.xml"/>
  <!-- 映射mapper文件 -->
  <property name="mapperLocations">
   <list>
    <value>classpath:conf/sqlMap/*.xml</value>
   </list>
  </property>
 </bean>    

 <!-- 获得sqlSession -->
 <bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">
  <constructor-arg name="sqlSessionFactory" ref="sqlSessionFactory"/>
 </bean>    

 <bean id="mapperScannerConfigurer" class="org.mybatis.spring.mapper.MapperScannerConfigurer">
  <!-- 这里的basePackage 指定了dao层接口路劲，这里的dao接口不用自己实现 -->
  <property name="basePackage" value="com.xiaoxi.dao" />
  <!-- 如果只有一个数据源的话可以不用指定，但是如果有多个数据源的话必须要指定 -->
  <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory" />
  <!--直接指定了sqlsessionTemplate名称，这个和上面的其实是一样的 -->
  <property name="sqlSessionTemplateBeanName" value="sqlSession" />
 </bean>
</beans>

六、log4j.properties配置

log4j.rootLogger=DEBUG, CATALINA# Define all the appenders
log4j.appender.CATALINA=org.apache.log4j.RollingFileAppender
log4j.appender.CATALINA.File=${catalina.base}/logs/catalina.log
log4j.appender.CATALINA.Append=true
log4j.appender.CATALINA.MaxFileSize=10MB
log4j.appender.CATALINA.Encoding=UTF-8

# Roll-over the log once per day
log4j.appender.CATALINA.layout = org.apache.log4j.PatternLayout
log4j.appender.CATALINA.layout.ConversionPattern = %d [%t] %-5p %c- %m%n
log4j.appender.LOCALHOST=org.apache.log4j.RollingFileAppender
log4j.appender.LOCALHOST.File=${catalina.base}/logs/localhost.log
log4j.appender.LOCALHOST.MaxFileSize=10MB
log4j.appender.LOCALHOST.Append=true
log4j.appender.LOCALHOST.Encoding=UTF-8
log4j.appender.LOCALHOST.layout = org.apache.log4j.PatternLayout
log4j.appender.LOCALHOST.layout.ConversionPattern = %d [%t] %-5p %c- %m%n

log4j.appender.MANAGER=org.apache.log4j.RollingFileAppender
log4j.appender.MANAGER.File=${catalina.base}/logs/manager.log
log4j.appender.MANAGER.MaxFileSize=10MB
log4j.appender.MANAGER.Append=true
log4j.appender.MANAGER.Encoding=UTF-8
log4j.appender.MANAGER.DatePattern='.'yyyy-MM-dd'.log'
log4j.appender.MANAGER.layout = org.apache.log4j.PatternLayout
log4j.appender.MANAGER.layout.ConversionPattern = %d [%t] %-5p %c- %m%n

log4j.appender.HOST-MANAGER=org.apache.log4j.RollingFileAppender
log4j.appender.HOST-MANAGER.File=${catalina.base}/logs/host-manager.log
log4j.appender.HOST-MANAGER.MaxFileSize=10MB
log4j.appender.HOST-MANAGER.Append=true
log4j.appender.HOST-MANAGER.Encoding=UTF-8
log4j.appender.HOST-MANAGER.DatePattern='.'yyyy-MM-dd'.log'
log4j.appender.HOST-MANAGER.layout = org.apache.log4j.PatternLayout
log4j.appender.HOST-MANAGER.layout.ConversionPattern = %d [%t] %-5p %c- %m%n

log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.Encoding=UTF-8
log4j.appender.CONSOLE.layout = org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern = %d [%t] %-5p %c- %m%n

# Configure which loggers log to which appenders
log4j.logger.org.apache.catalina.core.ContainerBase.[Catalina].[localhost]=INFO, LOCALHOST
log4j.logger.org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/manager]= INFO, MANAGER
log4j.logger.org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/host-manager]= INFO, HOST-MANAGER

七、相关路由数据源切换逻辑代码

package com.xiaoxi.config;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
import java.util.Map;

public class DynamicRoutingDataSource extends AbstractRoutingDataSource {

    @Override
    public void setTargetDataSources(Map<Object, Object> targetDataSources) {
        super.setTargetDataSources(targetDataSources);
        super.afterPropertiesSet();
    }

    @Override
    protected Object determineCurrentLookupKey() {
        return DataSourceContextHolder.getDbType();
    }
}

package com.xiaoxi.config;

/**
 * 线程上下文 <br>
 * 用于保存线程本地变量DbType(用于切换数据源)
 * 如果是异步线程操作，需要用InheritableThreadLocal （需要保存父线程的变量）
 *
 * @see [相关类/方法](可选)
 * @since [产品/模块版本](可选)
 */
public class DataSourceContextHolder {

    private static final ThreadLocal<DbType> contextHolder = new ThreadLocal<>();

    public static ThreadLocal<DbType> getLocal() {
        return contextHolder;
    }

    private DataSourceContextHolder () {}

    public static String getDbType() {
        return contextHolder.get() == null ? DbType.MASTER.dbType : contextHolder.get().dbType;
    }

    public static void setDbType(DbType dbType) {
        contextHolder.set(dbType);
    }

    public static void clearDbType() {
        contextHolder.remove();
    }

    public enum DbType {

        MASTER("Master"),

        SLAVE("Slave");

        private String dbType;

        DbType(String dbType) {
            this.dbType = dbType;
        }

        public String getDbType() {
            return dbType;
        }
    }
}

package com.xiaoxi.aop;

import com.xiaoxi.config.DataSourceContextHolder;
import org.apache.log4j.Logger;
import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.Pointcut;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

/**
 * 数据源切面，用于在执行sql前进行读写数据源切换 <br>
 * 〈功能详细描述〉
 *
 * @see [相关类/方法](可选)
 * @since [产品/模块版本](可选)
 */
@Aspect
@Order(-1)
@Component
public class DataSourceAop {

    private static Logger logger = Logger.getLogger(DataSourceAop.class);

    @Before("execution(* com.xiaoxi.dao..*.query*(..))")
    public void setReadDataSourceType() {
        DataSourceContextHolder.setDbType(DataSourceContextHolder.DbType.MASTER);
        logger.debug("[DataSourceAop] DataSource Covert To SLAVE");
    }

    @Before("execution(* com.xiaoxi.dao..*.insert*(..))" +
         "|| execution(* com.xiaoxi.dao..*.update*(..))" +
         "|| execution(* com.xiaoxi.dao..*.delete*(..))")
    public void setWriteDataSourceType() {
        DataSourceContextHolder.setDbType(DataSourceContextHolder.DbType.SLAVE);
        logger.debug("[DataSourceAop] DataSource Covert To MASTER");
    }

    /** ☆☆☆☆☆ 也可以获取参数中路由字段进行切换数据源 ☆☆☆☆☆ **/

    @Pointcut("execution(* com.xiaoxi.dao..*.*(..))")
    public void cutPoint() {}

    @Before(value="cutPoint()")
    public void setDynamicDataSource(JoinPoint point){
        String className = point.getTarget().getClass().getSimpleName();
        String methodName = point.getSignature().getName();
        String log = "[DataSourceAop] className:%s, methodName:%s";
        logger.debug(String.format(log, className, methodName));
    }
}

八、搭建过程中遇到的问题和解决方案

1、注入数据源dataSourceMaster和dataSourceSlave失败
spring 中jndiName配置的数据源名称和Tomcat配置文件中Resource name存在区别，并非一致,其中java:comp/env为环境，否则会报can not find jndi name …

2、Cannot create JDBC driver of class ‘' for connect URL ‘null'

3、The requested resource is not available（404）
分析了web.xml和servlet.xml发现配置无误，注解驱动和包扫描都配置，但仍然访问不了，后发现
项目启动过程中打印的日志存在问题，如下：
2019-12-17 16:20:41,767 [RMI TCP Connection(3)-127.0.0.1] INFO org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping- Mapped “{[/userInfo],methods=[GET]}” onto public java.lang.String com.xiaoxi.controller.UserInfoController.queryUserInfoById(java.lang.String)
通过分析发现这里的请求映射，通过controller的requestMapping映射到具体方法，却丢失了方法上的requestMapping路径，后发现方法RequestMapping写法如下：

@Controller
@RequestMapping("/userInfo")
public class UserInfoController {

    private static Logger logger =Logger.getLogger(UserInfoController.class);

    @Autowired
    private UserInfoService userInfoService;

    @ResponseBody
    @RequestMapping(name= "/queryUserInfoById", method = RequestMethod.GET)
    public String queryUserInfoById(@RequestParam("id") String id){
        logger.info("UserInfoController.queryUserInfoById.  id:{}" + id);
        UserInfo userInfo = userInfoService.queryUserInfoById(id);
        return JSON.toJSONString(userInfo);
    }
}

此处的RequestMapping属性name应该改为value，否则解析为空（可查看注解定义）

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