1、代码实现

import com.zaxxer.hikari.HikariDataSource;import lombok.Data;import lombok.Getter;import lombok.Setter;import org.aopalliance.intercept.MethodInvocation;import org.springframework.aop.Advisor;import org.springframework.aop.support.AbstractGenericPointcutAdvisor;import org.springframework.aop.support.AopUtils;import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;import org.springframework.boot.autoconfigure.jdbc.DataSourceProperties;import org.springframework.boot.context.properties.ConfigurationProperties;import org.springframework.boot.context.properties.EnableConfigurationProperties;import org.springframework.context.ApplicationContextAware;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.context.annotation.Primary;import org.springframework.core.Ordered;import org.springframework.core.annotation.Order;import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;import org.springframework.transaction.interceptor.TransactionAttribute;import org.springframework.transaction.interceptor.TransactionInterceptor;import javax.servlet.ServletRequestEvent;import javax.servlet.ServletRequestListener;import javax.sql.DataSource;import java.lang.reflect.Field;import java.util.Arrays;import java.util.HashMap;import java.util.Map;import java.util.concurrent.atomic.AtomicInteger;@Configuration("dynamicDataSourceConfig")@ConditionalOnProperty(name = "dynamic.jdbc", havingValue = "true")@EnableConfigurationProperties(value = DynamicDataSourceConfig.DynamicDataSourceProperties.class)public class DynamicDataSourceConfig {    /**     * 动态数据源     * @param dynamicDataSourceProperties     * @return     */    @Primary    @Bean("dynamicDataSource")    public DataSource dataSource(DynamicDataSourceProperties dynamicDataSourceProperties) {        JdbcDataSourceProperties[] jdbcDataSourceProperties = dynamicDataSourceProperties.getDatasources();        if (jdbcDataSourceProperties == null) {            throw new IllegalArgumentException("can not find any available dynamic.datasource config");        }        Map
    
      targetDataSources = new HashMap<>();        for (int i = 0; i < jdbcDataSourceProperties.length; ++i) {            JdbcDataSourceProperties properties = jdbcDataSourceProperties[i];            if (properties.getDatasourceId() == null || properties.getDatasourceId().trim().isEmpty()) {                throw new IllegalArgumentException("dynamic.jdbc.datasources[" + i + "].datasourceId can not be null");            }            if (targetDataSources.get(properties.getDatasourceId()) != null) {                throw new IllegalArgumentException("dynamic.jdbc.datasources[" + i + "].datasourceId already exists");            }            properties.setType(HikariDataSource.class);            targetDataSources.put(properties.getDatasourceId(), properties.initializeDataSourceBuilder().build());        }        DynamicDataSource dynamicDataSource = new DynamicDataSource();        dynamicDataSource.setTargetDataSources(targetDataSources);        String[] readers = Arrays.asList(jdbcDataSourceProperties)                .stream()                .filter(e -> JdbcDataSourceProperties.READ_ACCESS_TYPE.equals(e.accessType))                .map(JdbcDataSourceProperties::getDatasourceId)                .toArray(String[]::new);        String[] writers = Arrays.asList(jdbcDataSourceProperties)                .stream()                .filter(e -> JdbcDataSourceProperties.WRITE_ACCESS_TYPE.equals(e.accessType))                .map(JdbcDataSourceProperties::getDatasourceId)                .toArray(String[]::new);        dynamicDataSource.setReaders(readers.length > 0 ? readers : null);        dynamicDataSource.setWriters(writers.length > 0 ? writers : null);        return dynamicDataSource;    }    @Bean("dynamicDataSourceServletRequestListener")    @Order(Ordered.HIGHEST_PRECEDENCE)    public ServletRequestListener servletRequestListener() {        return new ServletRequestListener() {            @Override            public void requestDestroyed(ServletRequestEvent sre) {                DynamicDataSource.clearTransactionDatasource();            }            @Override            public void requestInitialized(ServletRequestEvent sre) {                DynamicDataSource.clearTransactionDatasource();            }        };    }    /**     * 对aop中的Advisor注入 TransactionInterceptor 的代理类     * @return     */    @Bean("dynamicDataSourceApplicationContextAware")    public ApplicationContextAware applicationContextAware() {        return (applicationContext -> {            applicationContext.getBeansOfType(Advisor.class).values().stream().forEach(advisor -> {                if (advisor.getAdvice() instanceof TransactionInterceptor) {                    TransactionInterceptorProxy proxy = new TransactionInterceptorProxy((TransactionInterceptor) advisor.getAdvice());                    //尝试设置代理类                    if (advisor instanceof AbstractGenericPointcutAdvisor) {                        ((AbstractGenericPointcutAdvisor) advisor).setAdvice(proxy);                    } else {                        //尝试通过反射代入                        try {                            Class
      clz = advisor.getClass();                            TransactionInterceptor interceptor = null;                            while (interceptor == null && clz != null && clz != Object.class) {                                for (Field f : clz.getDeclaredFields()) {                                    if (!f.isAccessible()) f.setAccessible(true);                                    Object advice = f.get(advisor);                                    if (advice == advisor.getAdvice()) {                                        interceptor = (TransactionInterceptor) advice;                                        f.set(advisor, proxy);                                        break;                                    }                                }                                clz = clz.getSuperclass();                            }                        } catch (Throwable t) {                            // skip                        }                    }                }            });        });    }    /**     * 多数据源配置     */    @ConfigurationProperties("dynamic.jdbc")    @Data    public static class DynamicDataSourceProperties {        private JdbcDataSourceProperties[] datasources;    }    /**     * 继承springboot的数据源配置     */    @Data    public static class JdbcDataSourceProperties extends DataSourceProperties {        public static final String READ_ACCESS_TYPE = "read";        public static final String WRITE_ACCESS_TYPE = "write";        //确保唯一        private String datasourceId;        //read 为读库，write 为写库，不配置为其他用途，比如生产环境配置相应的压力测试库等，        // 该类型的数据源不参与正常的业务处理，除非程序主动选择        private String accessType;    }    /**     * 数据源动态选择     */    public static class DynamicDataSource extends AbstractRoutingDataSource {        private static final ThreadLocal
     
       CURRENT_DATASOURCE = new ThreadLocal<>();        private static final ThreadLocal
      
        FORCE_DATASOURCE = new ThreadLocal<>();        //写库，如果操作进来的一个是写，后面是读，那么都强制走读库，避免主从延迟，获取不到最新的数据        private static final ThreadLocal
       
         CURRENT_WRITE_DATASOURCE = new ThreadLocal<>();        private static final ThreadLocal
        
          CURRENT_TRANSACTION = ThreadLocal.withInitial(() -> new AtomicInteger(0));        @Getter        @Setter        private static String[] readers;        @Getter        @Setter        private static String[] writers;        private static final AtomicInteger readerCounter = new AtomicInteger(0);        private static final AtomicInteger writerCounter = new AtomicInteger(0);        static String getReader() {            return readers != null ? readers[readerCounter.getAndIncrement() % readers.length] : null;        }        static String getWriter() {            return writers != null ? writers[writerCounter.getAndIncrement() % writers.length] : null;        }        /**         * 设置强制的数据源id         * @param datasourceId         */        public static void setCurrentDatasourceId(String datasourceId) {            if (CURRENT_DATASOURCE.get() == null) {                FORCE_DATASOURCE.set(datasourceId);            }        }        public static String getCurrentDatasourceId() {            return FORCE_DATASOURCE.get();        }        public static void setCurrentTransactionDatasource(TransactionAttribute transactionDatasource) {            CURRENT_TRANSACTION.get().incrementAndGet(); //添加事务记录            if (CURRENT_DATASOURCE.get() != null) return;//如果已经选中了，不重置，嵌套事务才会这样，service相互调用            //是否强制使用            if (FORCE_DATASOURCE.get() != null) {                CURRENT_DATASOURCE.set(FORCE_DATASOURCE.get());                return;            }            if (CURRENT_WRITE_DATASOURCE.get() != null) {                CURRENT_DATASOURCE.set(CURRENT_WRITE_DATASOURCE.get());                return;            }            //是否只读            boolean readOnly = transactionDatasource != null && transactionDatasource.isReadOnly();            String datasource = readOnly ? getReader() : getWriter();            //没有配置读库，走写库            if (datasource == null && readOnly) {                datasource = getWriter();            }            if (datasource == null) {                throw new IllegalArgumentException("can not find any datasource ");            }            if (!readOnly) {                CURRENT_WRITE_DATASOURCE.set(datasource);            }            CURRENT_DATASOURCE.set(datasource);        }        public static void reSetCurrentTransactionDatasource() {            AtomicInteger tras = CURRENT_TRANSACTION.get();            if (tras.get() == 0) return;// 不应该存在这种情况            int cnt = tras.decrementAndGet();            if (cnt > 0) return; //还有嵌套事务没有完成            CURRENT_DATASOURCE.set(null);        }        private static String getCurrentLookupKey() {            String key = CURRENT_DATASOURCE.get();            if (key == null) key = CURRENT_WRITE_DATASOURCE.get();            if (key == null) key = getReader();            if (key == null) key = getWriter();            return key;        }        static void clearTransactionDatasource() {            CURRENT_DATASOURCE.set(null);            FORCE_DATASOURCE.set(null);            CURRENT_WRITE_DATASOURCE.set(null);            CURRENT_TRANSACTION.get().set(0);        }        @Override        protected Object determineCurrentLookupKey() {            return getCurrentLookupKey();        }    }    public static class TransactionInterceptorProxy extends TransactionInterceptor {        private TransactionInterceptor source;        public TransactionInterceptorProxy(TransactionInterceptor transactionInterceptor) {            this.source = transactionInterceptor;        }        @Override        public Object invoke(MethodInvocation invocation) throws Throwable {            Class
          targetClass = (invocation.getThis() != null ? AopUtils.getTargetClass(invocation.getThis()) : null);            TransactionAttribute transactionAttribute = this.source.getTransactionAttributeSource().getTransactionAttribute(invocation.getMethod(), targetClass);            try {                if (transactionAttribute != null) DynamicDataSource.setCurrentTransactionDatasource(transactionAttribute);                return this.source.invoke(invocation);            } finally {                if (transactionAttribute != null) DynamicDataSource.reSetCurrentTransactionDatasource();            }        }    }}
        
       
      
     
    

2、配置

dynamic.jdbc=truedynamic.jdbc.datasources[0].datasourceId=firstdynamic.jdbc.datasources[0].url=jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=utf-8&allowMultiQueries=true&useSSL=falsedynamic.jdbc.datasources[0].username=readdynamic.jdbc.datasources[0].password=123456dynamic.jdbc.datasources[0].driver-class-name=com.mysql.cj.jdbc.Driver#read 为读库，write 为写库，不配置为其他用途，比如生产环境配置相应的压力测试库等dynamic.jdbc.datasources[0].accessType=readdynamic.jdbc.datasources[1].datasourceId=seconddynamic.jdbc.datasources[1].url=jdbc:mysql://127.0.0.1:3306/test2?useUnicode=true&characterEncoding=utf-8&allowMultiQueries=true&useSSL=falsedynamic.jdbc.datasources[1].username=readdynamic.jdbc.datasources[1].password=123456dynamic.jdbc.datasources[1].driver-class-name=com.mysql.cj.jdbc.Driverdynamic.jdbc.datasources[1].accessType=readdynamic.jdbc.datasources[2].datasourceId=thirddynamic.jdbc.datasources[2].url=jdbc:mysql://127.0.0.1:3306/test2?useUnicode=true&characterEncoding=utf-8&allowMultiQueries=true&useSSL=falsedynamic.jdbc.datasources[2].username=writedynamic.jdbc.datasources[2].password=123456dynamic.jdbc.datasources[2].driver-class-name=com.mysql.cj.jdbc.Driverdynamic.jdbc.datasources[2].accessType=write