基于JNDI 实现读写分离

我会带着你远行 2023-06-23 05:58 22阅读 0赞

**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：

**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**

**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" >    
    	
    	    
    	<bean id="dataSourceMaster" class="org.springframework.jndi.JndiObjectFactoryBean">        
    		<property name="jndiName" value="java:comp/env/dataSourceMaster"/>    
    	</bean>    
    	    
    	<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">        
    		        
    		<property name="dataSource" ref="dynamicDataSource"/>    
    	</bean>    
    	
    	<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">        
    		        
    		<property name="dataSource" ref="dynamicDataSource"/>        
    		        
    		<property name="configLocation" value="classpath:conf/spring/mybatis-config.xml"/>        
    		        
    		<property name="mapperLocations">            
    			<list>                
    				<value>classpath:conf/sqlMap/*.xml</value>            
    			</list>        
    		</property>    
    	</bean>    
    
    	    
    	<bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">        
    		<constructor-arg name="sqlSessionFactory" ref="sqlSessionFactory"/>    	
    	</bean>    
    
    	<bean id="mapperScannerConfigurer" class="org.mybatis.spring.mapper.MapperScannerConfigurer">        
    		        
    		<property name="basePackage" value="com.xiaoxi.dao" />        
    		        
    		<property name="sqlSessionFactoryBeanName" value="sqlSessionFactory" />        
    		        
    		<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）