方案一
通过Spring AOP在业务层实现读写分离，在DAO层定义切面，利用Spring的AbstractRoutingDataSource解决多数据源的问题，实现动态选择数据源
dao层代码如下：
public interface InvTsReturnStockDao {
@Master
Integer insert(InvTsReturnStock invTsReturnStock);
@Slave
List selectAll(@Param("status") String status);
}
执行流程：
1、调用insert();的方法时候，切面（Spring Aspect）先根据注解设置数据源类型。
2、然后需要获取数据库连接this.determineTargetDataSource().getConnection();this.determineTargetDataSource()获得选定的数据源。
实现过程：
- 1、定义多数据源
- 2、自定义路由数据源
public class ReadWriteRoutingDataSourceHolder {
private static final ThreadLocal holder = new ThreadLocal();
private static final ThreadLocal masterHolder = new ThreadLocal();
public static void put(String value) {
holder.set(value);
}
public static String get() {
if (null != masterHolder.get() && masterHolder.get()) {
return "";
}
return holder.get();
}
public static void clear() {
holder.remove();
}
/**
* 设置是否需要整个事务都需要主库
* @param isAlwaysMaster
*/
public static void setIsAlwaysMaster(Boolean isAlwaysMaster) {
masterHolder.set(isAlwaysMaster);
}
/**
* 清除整个事务需要主库设置
*/
public static void clearIsAlwaysMaster() {
masterHolder.remove();
}
}
通过ThreadLocal 来记录当前线程选择的数据源，通过切面去设置ThreadLocal当前线程选择的数据源.ThreadLocal是实现关键，使在整个线程调用过程中设置的数据源与别的线程隔离
public class ReadWriteRoutingDataSource extends AbstractRoutingDataSource {
private static final Logger LOGGER = LoggerFactory.getLogger(ReadWriteRoutingDataSource.class);
@Override
protected Object determineCurrentLookupKey() {
String routingDataSourceType = ReadWriteRoutingDataSourceHolder.get();
if (StringUtil.isEmpty(routingDataSourceType)) {
routingDataSourceType = RoutingDataSourceType.MASTER.toString();
}
ReadWriteRoutingDataSourceHolder.clear();
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("############## ReadWriteRoutingDataSource:" + routingDataSourceType
+ " ##############");
}
return routingDataSourceType;
}
}
determineCurrentLookupKey()方法，返回选择的数据源key，返回的数据源key是通过切面设置的
public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean {
private Map targetDataSources;
private Object defaultTargetDataSource;
private boolean lenientFallback = true;
private DataSourceLookup dataSourceLookup = new JndiDataSourceLookup();
private Map resolvedDataSources;
private DataSource resolvedDefaultDataSource;
public AbstractRoutingDataSource() {
}
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(DataSourceLookup dataSourceLookup) {
this.dataSourceLookup = (DataSourceLookup)(dataSourceLookup != null ? dataSourceLookup : new JndiDataSourceLookup());
}
//该bean 初始化的时候会调用
public void afterPropertiesSet() {
if (this.targetDataSources == null) {
throw new IllegalArgumentException("Property 'targetDataSources' is required");
} else {
this.resolvedDataSources = new HashMap(this.targetDataSources.size());
//遍历步骤1 第二段代码设置进去的数据源
Iterator var2 = this.targetDataSources.entrySet().iterator();
while(var2.hasNext()) {
Entry entry = (Entry)var2.next();
Object lookupKey = this.resolveSpecifiedLookupKey(entry.getKey());
DataSource dataSource = this.resolveSpecifiedDataSource(entry.getValue());
//将数据源以key-value 的形式放到resolvedDataSources中
this.resolvedDataSources.put(lookupKey, dataSource);
}
if (this.defaultTargetDataSource != null) {
this.resolvedDefaultDataSource = this.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);
}
}
//获取数据库连接
public Connection getConnection() throws SQLException {
return this.determineTargetDataSource().getConnection();
}
public Connection getConnection(String username, String password) throws SQLException {
return this.determineTargetDataSource().getConnection(username, password);
}
public T unwrap(Class iface) throws SQLException {
return iface.isInstance(this) ? this : this.determineTargetDataSource().unwrap(iface);
}
public boolean isWrapperFor(Class iface) throws SQLException {
return iface.isInstance(this) || this.determineTargetDataSource().isWrapperFor(iface);
}
//获取数据源
protected DataSource determineTargetDataSource() {
Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");
//调用第一段代码获得选中的
Object lookupKey = this.determineCurrentLookupKey();
DataSource dataSource =
//获得数据源的key
(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 + "]");
} else {
return dataSource;
}
}
protected abstract Object determineCurrentLookupKey();
}
- 3、定义注解
@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
public @interface Master {
}
- 4、定义切面
@Aspect
public class ReadWriteRoutingDataSourceAspect {
private static final Logger LOGGER = LoggerFactory
.getLogger(ReadWriteRoutingDataSourceAspect.class);
/**
* Map>
*/
private static final Map> classMethodSourceMap = new ConcurrentHashMap>();
//该切面切所有dao层方法
@Pointcut("execution(* com.haier.cbs.*.dao.*.*(..))")
public void daoPointcut() {
}
/**
* 根据Dao的数据源注解注入数据源
* {@link RoutingDataSource} 优先级低于{@link Slave}和{@link Master}
* {@link RoutingDataSource} 暂时不支持按数据源标识选择数据源，所以现在的版本中此此注解可以忽略
* @param joinPoint joinPoint
*/
@Before("daoPointcut()")
public void before(JoinPoint joinPoint) {
Object target = joinPoint.getTarget();
MethodSignature methodSignature = (MethodSignature) joinPoint.getSignature();
Method method = methodSignature.getMethod();
Class clazz = target.getClass();
String routingDataSourceType;
Map methodSourceMap;
String className;
Class[] interfaces = clazz.getInterfaces();
if (null != interfaces && interfaces.length > 0) {
className = clazz.getInterfaces()[0].getName();
} else {
className = clazz.getName();
}
String methodName = method.getName();
if (classMethodSourceMap.containsKey(className)) {
methodSourceMap = classMethodSourceMap.get(className);
} else {
methodSourceMap = new ConcurrentHashMap();
classMethodSourceMap.put(className, methodSourceMap);
}
if (methodSourceMap.containsKey(methodName)) {
routingDataSourceType = methodSourceMap.get(methodName);
} else {
Master master;
Slave slave;
master = AnnotationUtils.findAnnotation(method, Master.class);
slave = AnnotationUtils.findAnnotation(method, Slave.class);
if (master == null && slave == null) {
master = AnnotationUtils.findAnnotation(clazz, Master.class);
slave = AnnotationUtils.findAnnotation(clazz, Slave.class);
}
if (master != null && slave != null) {
throw new IllegalArgumentException("不能同时指定MASTER和SLAVE");
}
routingDataSourceType = master == null ? slave == null ? null
: RoutingDataSourceType.SLAVE.toString() : RoutingDataSourceType.MASTER.toString();
if (routingDataSourceType == null) {
RoutingDataSource routingDataSource;
routingDataSource = AnnotationUtils.findAnnotation(method, RoutingDataSource.class);
if (routingDataSource == null) {
routingDataSource = AnnotationUtils.findAnnotation(clazz,
RoutingDataSource.class);
}
if (routingDataSource != null) {
routingDataSourceType = routingDataSource.type().toString();
}
}
if (routingDataSourceType == null) {
routingDataSourceType = RoutingDataSourceType.MASTER.toString();
}
methodSourceMap.put(methodName, routingDataSourceType);
}
//将选用的数据源放到ThreadLocal中
ReadWriteRoutingDataSourceHolder.put(routingDataSourceType);
if (LOGGER.isDebugEnabled()) {
String interfaceName = clazz.getInterfaces().length > 0 ? clazz.getInterfaces()[0]
.getName() : "UNKNOWN";
LOGGER.debug("***** [" + interfaceName + "." + method.getName()
+ "] route DataSource to " + routingDataSourceType + " *****");
}
}
@After("daoPointcut()")
public void after(JoinPoint joinPoint) {
ReadWriteRoutingDataSourceHolder.clear();
if (LOGGER.isDebugEnabled()) {
Object target = joinPoint.getTarget();
Class clazz = target.getClass();
MethodSignature methodSignature = (MethodSignature) joinPoint.getSignature();
Method method = methodSignature.getMethod();
String interfaceName = clazz.getInterfaces().length > 0 ? clazz.getInterfaces()[0]
.getName() : "UNKNOWN";
LOGGER.debug("***** [" + interfaceName + "." + method.getName() + "] cleared *****");
}
}
}