Java基于JNDI怎么实现读写分离

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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）：

 dataSourceMaster javax.sql.DataSource  Container dataSourceSlave javax.sql.DataSource Container

三、web.xml配置

   Archetype Created Web Application         log4jConfigLocation      classpath:log4j.properties              log4jRefreshInterval      60000            CharacterEncodingFilter      org.springframework.web.filter.CharacterEncodingFilter                encoding         utf-8                     forceEncoding         true                  CharacterEncodingFilter      xiyun            xiyun      org.springframework.web.servlet.DispatcherServlet               contextConfigLocation                 classpath:conf/spring/spring-servlet.xml                  1            xiyun      *.do   

四、spring-servlet.xml配置

五、spring-db.xml配置

                                                                                                                                                                                                                                                            classpath:conf/sqlMap/*.xml                                                                                                                              

六、log4j.properties配置

log4j.rootLogger=DEBUG, CATALINA# Define all the appenderslog4j.appender.CATALINA=org.apache.log4j.RollingFileAppenderlog4j.appender.CATALINA.File=${catalina.base}/logs/catalina.loglog4j.appender.CATALINA.Append=truelog4j.appender.CATALINA.MaxFileSize=10MBlog4j.appender.CATALINA.Encoding=UTF-8# Roll-over the log once per daylog4j.appender.CATALINA.layout = org.apache.log4j.PatternLayoutlog4j.appender.CATALINA.layout.ConversionPattern = %d [%t] %-5p %c- %m%nlog4j.appender.LOCALHOST=org.apache.log4j.RollingFileAppenderlog4j.appender.LOCALHOST.File=${catalina.base}/logs/localhost.loglog4j.appender.LOCALHOST.MaxFileSize=10MBlog4j.appender.LOCALHOST.Append=truelog4j.appender.LOCALHOST.Encoding=UTF-8log4j.appender.LOCALHOST.layout = org.apache.log4j.PatternLayoutlog4j.appender.LOCALHOST.layout.ConversionPattern = %d [%t] %-5p %c- %m%nlog4j.appender.MANAGER=org.apache.log4j.RollingFileAppenderlog4j.appender.MANAGER.File=${catalina.base}/logs/manager.loglog4j.appender.MANAGER.MaxFileSize=10MBlog4j.appender.MANAGER.Append=truelog4j.appender.MANAGER.Encoding=UTF-8log4j.appender.MANAGER.DatePattern='.'yyyy-MM-dd'.log'log4j.appender.MANAGER.layout = org.apache.log4j.PatternLayoutlog4j.appender.MANAGER.layout.ConversionPattern = %d [%t] %-5p %c- %m%nlog4j.appender.HOST-MANAGER=org.apache.log4j.RollingFileAppenderlog4j.appender.HOST-MANAGER.File=${catalina.base}/logs/host-manager.loglog4j.appender.HOST-MANAGER.MaxFileSize=10MBlog4j.appender.HOST-MANAGER.Append=truelog4j.appender.HOST-MANAGER.Encoding=UTF-8log4j.appender.HOST-MANAGER.DatePattern='.'yyyy-MM-dd'.log'log4j.appender.HOST-MANAGER.layout = org.apache.log4j.PatternLayoutlog4j.appender.HOST-MANAGER.layout.ConversionPattern = %d [%t] %-5p %c- %m%nlog4j.appender.CONSOLE=org.apache.log4j.ConsoleAppenderlog4j.appender.CONSOLE.Encoding=UTF-8log4j.appender.CONSOLE.layout = org.apache.log4j.PatternLayoutlog4j.appender.CONSOLE.layout.ConversionPattern = %d [%t] %-5p %c- %m%n# Configure which loggers log to which appenderslog4j.logger.org.apache.catalina.core.ContainerBase.[Catalina].[localhost]=INFO, LOCALHOSTlog4j.logger.org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/manager]= INFO, MANAGERlog4j.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 targetDataSources) {        super.setTargetDataSources(targetDataSources);        super.afterPropertiesSet();    }    @Override    protected Object determineCurrentLookupKey() {        return DataSourceContextHolder.getDbType();    }}

package com.xiaoxi.config;/** * 线程上下文 
 * 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 contextHolder = new ThreadLocal<>();    public static ThreadLocal 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 
 * 〈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)@Componentpublic 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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