背景
數據庫配置主從之后，如何在代碼層面實現讀寫分離？
用戶自定義設置數據庫路由
Spring boot提供了AbstractRoutingDataSource根據用戶定義的規則選擇當前的數據庫，這樣我們可以在執行查詢之前，設置讀取從庫，在執行完成后，恢復到主庫。
實現可動態路由的數據源，在每次數據庫查詢操作前執行
ReadWriteSplitRoutingDataSource.java
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;/** * @author songrgg * @since 1.0 */public class ReadWriteSplitRoutingDataSource extends AbstractRoutingDataSource { @Override protected Object determineCurrentLookupKey() { return DbContextHolder.getDbType(); }}線程私有路由配置，用于ReadWriteSplitRoutingDataSource動態讀取配置
DbContextHolder.java
/** * @author songrgg * @since 1.0 */public class DbContextHolder { public enum DbType { MASTER, SLAVE } private static final ThreadLocal<DbType> contextHolder = new ThreadLocal<>(); public static void setDbType(DbType dbType) { if(dbType == null){ throw new NullPointerException(); } contextHolder.set(dbType); } public static DbType getDbType() { return contextHolder.get() == null ? DbType.MASTER : contextHolder.get(); } public static void clearDbType() { contextHolder.remove(); }}AOP優化代碼
利用AOP將設置數據庫的操作從代碼中抽離，這里的粒度控制在方法級別，所以利用注解的形式標注這個方法涉及的數據庫事務只讀，走從庫。
只讀注解，用于標注方法的數據庫操作只走從庫。
ReadOnlyConnection.java
package com.wallstreetcn.hatano.config;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;/** * Indicates the database operations is bound to the slave database. * AOP interceptor will set the database to the slave with this interface. * @author songrgg * @since 1.0 */@Target({ElementType.METHOD, ElementType.TYPE})@Retention(RetentionPolicy.RUNTIME)public @interface ReadOnlyConnection {}ReadOnlyConnectionInterceptor.java
import org.aspectj.lang.ProceedingJoinPoint;import org.aspectj.lang.annotation.Around;import org.aspectj.lang.annotation.Aspect;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.core.Ordered;import org.springframework.stereotype.Component;/** * Intercept the database operations, bind database to read-only database as this annotation * is applied. * @author songrgg * @since 1.0 */@Aspect@Componentpublic class ReadOnlyConnectionInterceptor implements Ordered { private static final Logger logger = LoggerFactory.getLogger(ReadOnlyConnectionInterceptor.class); @Around("@annotation(readOnlyConnection)") public Object proceed(ProceedingJoinPoint proceedingJoinPoint, ReadOnlyConnection readOnlyConnection) throws Throwable { try { logger.info("set database connection to read only"); DbContextHolder.setDbType(DbContextHolder.DbType.SLAVE); Object result = proceedingJoinPoint.proceed(); return result; } finally { DbContextHolder.clearDbType(); logger.info("restore database connection"); } } @Override public int getOrder() { return 0; }}UserService.java
@ReadOnlyConnectionpublic List<User> getUsers(Integer page, Integer limit) { return repository.findAll(new PageRequest(page, limit));}配置Druid數據庫連接池
build.gradle
compile("com.alibaba:druid:1.0.18")
groovy依賴注入
配置dataSource為可路由數據源
context.groovy
import com.alibaba.druid.pool.DruidDataSourceimport DbContextHolderimport ReadWriteSplitRoutingDataSource** SOME INITIALIZED CODE LOAD PROPERTIES **def dataSourceMaster = new DruidDataSource()dataSourceMaster.url = properties.get('datasource.master.url')println("master set to " + dataSourceMaster.url)dataSourceMaster.username = properties.get('datasource.master.username')dataSourceMaster.password = properties.get('datasource.master.password')def dataSourceSlave = new DruidDataSource()dataSourceSlave.url = properties.get('datasource.slave.url')println("slave set to " + dataSourceSlave.url)dataSourceSlave.username = properties.get('datasource.slave.username')dataSourceSlave.password = properties.get('datasource.slave.password') beans { dataSource(ReadWriteSplitRoutingDataSource) { bean -> targetDataSources = [ (DbContextHolder.DbType.MASTER): dataSourceMaster, (DbContextHolder.DbType.SLAVE): dataSourceSlave ] }}以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持武林網。
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