环境：springboot2.2.6RELEASE
实现目标：一写多读，读可以任意配置多个，默认都是从写库中进行操作，只有符合条件的方法(指定的目标方法或者标有指定注解的方法才会从读库中操作)。独立打成一个jar包放入本地仓库。
实现原理：通过aop。
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<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-configuration-processor</artifactId> <optional>true</optional> </dependency>
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pack: datasource: pointcut: execution(public * net.greatsoft.service.base.*.*(..)) || execution(public * net.greatsoft.service.xxx.*.*(..)) master: driverClassName: oracle.jdbc.driver.OracleDriver jdbcUrl: jdbc:oracle:thin:@10.100.102.113:1521/orcl username: test password: test minimumIdle: 10 maximumPoolSize: 200 autoCommit: true idleTimeout: 30000 poolName: MbookHikariCP maxLifetime: 1800000 connectionTimeout: 30000 connectionTestQuery: SELECT 1 FROM DUAL slaves: - driverClassName: oracle.jdbc.driver.OracleDriver jdbcUrl: jdbc:oracle:thin:@10.100.102.113:1521/orcl username: dc password: dc minimumIdle: 10 maximumPoolSize: 200 autoCommit: true idleTimeout: 30000 poolName: MbookHikariCP maxLifetime: 1800000 connectionTimeout: 30000 connectionTestQuery: SELECT 1 FROM DUAL - driverClassName: oracle.jdbc.driver.OracleDriver jdbcUrl: jdbc:oracle:thin:@10.100.102.113:1521/orcl username: empi password: empi minimumIdle: 10 maximumPoolSize: 200 autoCommit: true idleTimeout: 30000 poolName: MbookHikariCP maxLifetime: 1800000 connectionTimeout: 30000 connectionTestQuery: SELECT 1 FROM DUAL
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pointcut：定义切点，那些方法是需要拦截(从读库中操作)。
master：写库配置。
slaves：读库配置(List集合)。
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![[[389704]]](https://s6.51cto.com/oss/202103/26/bfc2457ae79fc43de26d328332560d8d.png){kind=link}
@Component @ConfigurationProperties(prefix = "pack.datasource") public class RWDataSourceProperties { private String pointcut ; private HikariConfig master ; private List<HikariConfig> slaves = new ArrayList<>(); }
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public class RWConfig { private static Logger logger = LoggerFactory.getLogger(RWConfig.class) ; @Bean public HikariDataSource masterDataSource(RWDataSourceProperties rwDataSourceProperties) { return new HikariDataSource(rwDataSourceProperties.getMaster()) ; } @Bean public List<HikariDataSource> slaveDataSources(RWDataSourceProperties rwDataSourceProperties) { List<HikariDataSource> lists = new ArrayList<>() ; for(HikariConfig config : rwDataSourceProperties.getSlaves()) { lists.add(new HikariDataSource(config)) ; } return lists ; } @Bean @Primary @DependsOn({"masterDataSource", "slaveDataSources"}) public AbstractRoutingDataSource routingDataSource(@Qualifier("masterDataSource")DataSource masterDataSource, @Qualifier("slaveDataSources")List<HikariDataSource> slaveDataSources) { BaseRoutingDataSource ds = new BaseRoutingDataSource() ; Map<Object, Object> targetDataSources = new HashMap<>(2) ; targetDataSources.put("master", masterDataSource) ; for (int i = 0; i < slaveDataSources.size(); i++) { targetDataSources.put("slave-" + i, slaveDataSources.get(i)) ; } ds.setDefaultTargetDataSource(masterDataSource) ; ds.setTargetDataSources(targetDataSources) ; return ds ; } }
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public class BaseRoutingDataSource extends AbstractRoutingDataSource { @Resource private DataSourceHolder holder; @Override protected Object determineCurrentLookupKey() { return holder.get() ; } }
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public class DataSourceHolder { private ThreadLocal<Integer> context = new ThreadLocal<Integer>() { @Override protected Integer initialValue() { return 0 ; } }; @Resource private BaseSlaveLoad slaveLoad ; public String get() { Integer type = context.get() ; return type == null || type == 0 ? "master" : "slave-" + slaveLoad.load() ; } public void set(Integer type) { context.set(type) ; } }
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通过aop动态设置context的内容值，0为从写库中操作，其它的都在读库中操作。
BaseSlaveLoad类为到底从那个读库中选取的一个算法类，默认实现使用的是轮询算法。
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public interface BaseSlaveLoad { int load() ; }
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public abstract class AbstractSlaveLoad implements BaseSlaveLoad { @Resource protected List<HikariDataSource> slaveDataSources ; }
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这里定义一个抽象类注入了读库列表，所有的实现类从该类中继承即可。
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public class PollingLoad extends AbstractSlaveLoad { private int index = 0 ; private int size = 1 ; @PostConstruct public void init() { size = slaveDataSources.size() ; } @Override public int load() { int n = index ; synchronized (this) { index = (++index) % size ; } return n ; } }
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配置成Bean
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@Bean @ConditionalOnMissingBean public BaseSlaveLoad slaveLoad() { return new PollingLoad() ; } @Bean public DataSourceHolder dataSourceHolder() { return new DataSourceHolder() ; }
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public class DataSourceAspect implements MethodInterceptor { private DataSourceHolder holder ; public DataSourceAspect(DataSourceHolder holder) { this.holder = holder ; } @Override public Object invoke(MethodInvocation invocation) throws Throwable { Method method = invocation.getMethod() ; String methodName = method.getName() ; SlaveDB slaveDB = method.getAnnotation(SlaveDB.class) ; if (slaveDB == null) { slaveDB = method.getDeclaringClass().getAnnotation(SlaveDB.class) ; } if (methodName.startsWith("find") || methodName.startsWith("get") || methodName.startsWith("query") || methodName.startsWith("select") || methodName.startsWith("list") || slaveDB != null) { holder.set(1) ; } else { holder.set(0) ; } return invocation.proceed(); } }
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应该切点需要动态配置，所以这里采用spring aop的方式来配置
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@Bean public AspectJExpressionPointcutAdvisor logAdvisor(RWDataSourceProperties props, DataSourceHolder holder) { AspectJExpressionPointcutAdvisor advisor = new AspectJExpressionPointcutAdvisor() ; logger.info("执行表达式：{}", props.getPointcut()) ; advisor.setExpression(props.getPointcut()) ; advisor.setAdvice(new DataSourceAspect(holder)) ; return advisor ; }
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public class RWImportSelector implements ImportSelector { @Override public String[] selectImports(AnnotationMetadata importingClassMetadata) { return new String[] {RWConfig.class.getName()} ; } }
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这里的RWConfig为我们上面的配置类
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@Retention(RetentionPolicy.RUNTIME) @Target(ElementType.TYPE) @Documented @Import({RWImportSelector.class}) public @interface EnableRW { }
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@Documented @Retention(RUNTIME) @Target({ TYPE, METHOD }) public @interface SlaveDB { }
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有@SlaveDB的注解方法会类都会从读库中操作。
到此读写分离组件开发完成。
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mvn install -Dmaven.test.skip=true
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引入依赖
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<dependency> <groupId>com.pack</groupId> <artifactId>xg-component-rw</artifactId> <version>1.0.0</version> </dependency>
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启动类添加注解开启读写分离功能
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@SpringBootApplication @EnableRW public class BaseWebApplication { public static void main(String[] args) { SpringApplication.run(BaseWebApplication.class, args); } }
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测试：
第一次查询：
第二次查询：
为了区别两个从库设置不同的数据
这里是写库
完毕！！！