二、拓扑图 三、代码实现 1.maven依赖
- 配置多个数据源。
- 将多个数据源放入map，map放入动态数据源，设定动态数据源的默认数据源。
- sqlSessionFactory中设定动态数据源。
- 动态数据源从threadLocal中获取目标数据源的名称，进而切换数据源。
- 通过aop切入方法，并约定好方法命名（注意this会使aop失效），来区分读和写。
- 前置通知中，读操作，threadLocal中放入读数据源的key；写操作，threadLocal中放入写数据源的key。
- 后置通知中，清空threadLocal，防止内存泄漏。
2.配置文件org.springframework.boot spring-boot-starter-weborg.springframework.boot spring-bootorg.projectlombok lombokmysql mysql-connector-javaruntime org.mybatis.spring.boot mybatis-spring-boot-starter1.3.0 com.alibaba druid-spring-boot-starter1.1.9 org.springframework.boot spring-boot-starter-aop
spring:
datasource:
type: com.alibaba.druid.pool.DruidDataSource
druid:
master:
name: masterDataSource
driver-class-name: com.mysql.jdbc.Driver
url: jdbc:mysql://10.200.242.87:8066/yxh_user?zeroDateTimeBehavior=convertToNull
username: root
password: root
slaver:
name: slaverDataSource
driver-class-name: com.mysql.jdbc.Driver
url: jdbc:mysql://127.0.0.1:3306/yxh_user?zeroDateTimeBehavior=convertToNull
username: root
password: root
3.枚举标识数据源名称
public enum DataSourceKey {
masterDataSource,
slaverDataSource
;
}
4.Threadlocal存放数据源名称
public class DynamicDataSourceContextHolder {
private static final ThreadLocal DB_CONTEXT_HOLDER = new ThreadLocal<>();
public static void setDataSourceKey(String key){
DB_CONTEXT_HOLDER.set(key);
}
public static String getDataSourceKey(){
return DB_CONTEXT_HOLDER.get();
}
public static void clearDataSourceKey(){
DB_CONTEXT_HOLDER.remove();
}
}
5.动态数据源类
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
public class DynamicRoutingDataSource extends AbstractRoutingDataSource {
@Override
protected Object determineCurrentLookupKey() {
return DynamicDataSourceContextHolder.getDataSourceKey();
}
}
6.配置类
import com.alibaba.druid.spring.boot.autoconfigure.DruidDataSourceBuilder;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.SqlSessionTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.io.DefaultResourceLoader;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import javax.sql.DataSource;
import java.util.HashMap;
import java.util.Map;
@Configuration
public class DataSourceConfigurer {
@Bean("masterDataSource")
@Primary
@ConfigurationProperties(prefix = "spring.datasource.druid.master")
public DataSource masterDataSource() {
return DruidDataSourceBuilder.create().build();
}
@Bean("slaverDataSource")
@ConfigurationProperties(prefix = "spring.datasource.druid.slaver")
public DataSource slaverDataSource() {
return DruidDataSourceBuilder.create().build();
}
@Bean("dynamicDataSource")
@Autowired
public DataSource dynamicDataSource(@Qualifier("masterDataSource") DataSource masterDataSource, @Qualifier("slaverDataSource")DataSource slaverDataSource) {
DynamicRoutingDataSource dynamicRoutingDataSource = new DynamicRoutingDataSource();
Map dataSourceMap = new HashMap<>();
dataSourceMap.put(DataSourceKey.masterDataSource.name(), masterDataSource);
dataSourceMap.put(DataSourceKey.slaverDataSource.name(), slaverDataSource);
dynamicRoutingDataSource.setTargetDataSources(dataSourceMap);
dynamicRoutingDataSource.setDefaultTargetDataSource(masterDataSource);
return dynamicRoutingDataSource;
}
@Bean("sqlSessionFactory")
@Autowired
public SqlSessionFactory sqlSessionFactoryBean(@Qualifier("dynamicDataSource") DataSource dynamicDataSource) throws Exception {
DefaultResourceLoader defaultResourceLoader = new DefaultResourceLoader();
SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
sqlSessionFactoryBean.setDataSource(dynamicDataSource);
sqlSessionFactoryBean.setConfigLocation(defaultResourceLoader.getResource("classpath:mybatis-config.xml"));
return sqlSessionFactoryBean.getObject();
}
@Autowired
@Bean
public SqlSessionTemplate sqlSessionTemplate(@Qualifier("sqlSessionFactory") SqlSessionFactory sqlSessionFactory) {
return new SqlSessionTemplate(sqlSessionFactory);
}
@Autowired
@Bean
public DataSourceTransactionManager txManager(@Qualifier("dynamicDataSource") DataSource dynamicDataSource) {
DataSourceTransactionManager txManager = new DataSourceTransactionManager();
txManager.setDataSource(dynamicDataSource);
return txManager;
}
}
7.AOP
@Component
@Aspect
public class DynamicDataSourceAspect {
private final List READ_PREFIX = Arrays.asList("query", "select", "get", "find");
private final List WRITE_PREFIX = Arrays.asList("add", "insert","update","modify", "delete", "remove");
@Pointcut("execution(* com.yxh.service..*.*(..))")
public void daoAspect() {}
@Before("daoAspect()")
public void switchDataSource(JoinPoint point) {
String methodName = point.getSignature().getName();
if (isReadMethod(methodName)) {
DynamicDataSourceContextHolder.setDataSourceKey(DataSourceKey.slaverDataSource.name());
} else if(isWriteMethod(methodName)){
DynamicDataSourceContextHolder.setDataSourceKey(DataSourceKey.masterDataSource.name());
}else {
DynamicDataSourceContextHolder.setDataSourceKey(DataSourceKey.masterDataSource.name());
}
}
@After("daoAspect()")
public void clearDataSource(JoinPoint point) {
DynamicDataSourceContextHolder.clearDataSourceKey();
}
public boolean isReadMethod(String methodName){
if(StringUtils.isBlank(methodName)){
return false;
}
for(String prefix : READ_PREFIX){
if(StringUtils.isNotBlank(prefix) && methodName.startsWith(prefix)){
return true;
}
}
return false;
}
public boolean isWriteMethod(String methodName){
if(StringUtils.isBlank(methodName)){
return false;
}
for(String prefix : WRITE_PREFIX){
if(StringUtils.isNotBlank(prefix) && methodName.startsWith(prefix)){
return true;
}
}
return false;
}
}
四、简单分析AbstractRoutingDataSource源码
自定义的数据源继承了AbstractRoutingDataSource，并重写了determineCurrentLookupKey()来获取目标数据源的名称。
先贴一波AbstractRoutingDataSource的源码供大家参考。
package org.springframework.jdbc.datasource.lookup;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;
import javax.sql.DataSource;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.jdbc.datasource.AbstractDataSource;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean {
@Nullable
private Map targetDataSources;
@Nullable
private Object defaultTargetDataSource;
private boolean lenientFallback = true;
private DataSourceLookup dataSourceLookup = new JndiDataSourceLookup();
@Nullable
private Map resolvedDataSources;
@Nullable
private DataSource resolvedDefaultDataSource;
public void setTargetDataSources(Map targetDataSources) {
this.targetDataSources = targetDataSources;
}
public void setDefaultTargetDataSource(Object defaultTargetDataSource) {
this.defaultTargetDataSource = defaultTargetDataSource;
}
public void setLenientFallback(boolean lenientFallback) {
this.lenientFallback = lenientFallback;
}
public void setDataSourceLookup(@Nullable DataSourceLookup dataSourceLookup) {
this.dataSourceLookup = (dataSourceLookup != null ? dataSourceLookup : new JndiDataSourceLookup());
}
@Override
public void afterPropertiesSet() {
if (this.targetDataSources == null) {
throw new IllegalArgumentException("Property 'targetDataSources' is required");
}
this.resolvedDataSources = new HashMap<>(this.targetDataSources.size());
this.targetDataSources.forEach((key, value) -> {
Object lookupKey = resolveSpecifiedLookupKey(key);
DataSource dataSource = resolveSpecifiedDataSource(value);
this.resolvedDataSources.put(lookupKey, dataSource);
});
if (this.defaultTargetDataSource != null) {
this.resolvedDefaultDataSource = resolveSpecifiedDataSource(this.defaultTargetDataSource);
}
}
protected Object resolveSpecifiedLookupKey(Object lookupKey) {
return lookupKey;
}
protected DataSource resolveSpecifiedDataSource(Object dataSource) throws IllegalArgumentException {
if (dataSource instanceof DataSource) {
return (DataSource) dataSource;
}
else if (dataSource instanceof String) {
return this.dataSourceLookup.getDataSource((String) dataSource);
}
else {
throw new IllegalArgumentException(
"Illegal data source value - only [javax.sql.DataSource] and String supported: " + dataSource);
}
}
@Override
public Connection getConnection() throws SQLException {
return determineTargetDataSource().getConnection();
}
@Override
public Connection getConnection(String username, String password) throws SQLException {
return determineTargetDataSource().getConnection(username, password);
}
@Override
@SuppressWarnings("unchecked")
public T unwrap(Class iface) throws SQLException {
if (iface.isInstance(this)) {
return (T) this;
}
return determineTargetDataSource().unwrap(iface);
}
@Override
public boolean isWrapperFor(Class iface) throws SQLException {
return (iface.isInstance(this) || determineTargetDataSource().isWrapperFor(iface));
}
protected DataSource determineTargetDataSource() {
Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");
// 获取目标数据源名称
Object lookupKey = determineCurrentLookupKey();
// 获取目标数据源
DataSource dataSource = this.resolvedDataSources.get(lookupKey);
if (dataSource == null && (this.lenientFallback || lookupKey == null)) {
dataSource = this.resolvedDefaultDataSource;
}
if (dataSource == null) {
throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]");
}
return dataSource;
}
@Nullable
protected abstract Object determineCurrentLookupKey();
}
AbstractRoutingDataSource中的determineTargetDataSource()中，使用模板方法设计模式，将determineCurrentLookupKey()抽象，供调用者灵活配置。我们一起看下determineTargetDataSource()的源码
protected DataSource determineTargetDataSource() {
Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");
// 获取目标数据源名称
Object lookupKey = determineCurrentLookupKey();
// 获取目标数据源
DataSource dataSource = this.resolvedDataSources.get(lookupKey);
if (dataSource == null && (this.lenientFallback || lookupKey == null)) {
dataSource = this.resolvedDefaultDataSource;
}
if (dataSource == null) {
throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]");
}
return dataSource;
}
resolvedDataSources其实是复制并加工了targetDataSources的内容，参考afterPropertiesSet()方法。而targetDataSources的赋值基于public void setTargetDataSources(Map
也就是最开始我们在配置类DataSourceConfigurer中创建自定义的动态数据源时调用了setTargetDataSources，放入的数据源map。
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