有時候在專案中會遇到需要連接兩個資料庫的情況，本文就結合Spring和Mybatis來講下怎么使用雙資料源（或者是多資料源），
背景知識介紹
本文中實作多資料源的關鍵是Spring提供的AbstractRoutingDataSource，這個類可以根據lookup key來實作底層資料源的動態轉換，
public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean {
@Nullable
private Map<Object, Object> targetDataSources;
@Nullable
private Object defaultTargetDataSource;
private boolean lenientFallback = true;
private DataSourceLookup dataSourceLookup = new JndiDataSourceLookup();
@Nullable
private Map<Object, DataSource> resolvedDataSources;
@Nullable
private DataSource resolvedDefaultDataSource;
public void setTargetDataSources(Map<Object, Object> 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> T unwrap(Class<T> 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");
Object lookupKey = determineCurrentLookupKey();
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
//一般只需要用戶實作這個方法，
protected abstract Object determineCurrentLookupKey();
}
實作流程
step1：實作一個自定義的AbstractRoutingDataSource
public class DynamicDataSource extends AbstractRoutingDataSource {
//這邊定義了一個和執行緒系結的ThreadLocal變數，用于存放需要使用的資料源的名稱
private static final ThreadLocal<String> dataSourceNameHolder = new ThreadLocal<>();
public DynamicDataSource(DataSource defaultTargetDataSource, Map<Object, Object> targetDataSources) {
super.setDefaultTargetDataSource(defaultTargetDataSource);
super.setTargetDataSources(targetDataSources);
super.afterPropertiesSet();
}
@Override
//重寫了AbstractRoutingDataSource的determineCurrentLookupKey方法
protected Object determineCurrentLookupKey() {
return getDataSource();
}
public static void setDataSource(String dataSource) {
dataSourceNameHolder.set(dataSource);
}
public static String getDataSource() {
return dataSourceNameHolder.get();
}
public static void clearDataSource() {
dataSourceNameHolder.remove();
}
}
step2：實作一個AOP對Service層方法進行AOP攔截，呼叫DynamicDataSource中的ThreadLocal變數，將當前請求需要使用的資料源名稱設定進去，
//定義一個DataSource注解
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface DataSource {
String name() default "";
}
//這邊再定義一個常量
public interface DataSourceNames {
String FIRST = "first";
String SECOND = "second";
}
定義AOP處理DataSource注解
@Aspect
@Component
public class DataSourceAspect implements Ordered {
protected Logger logger = LoggerFactory.getLogger(getClass());
@Pointcut("@annotation(com.xx.yy.annotation.DataSource)")
public void dataSourcePointCut() {
}
@Around("dataSourcePointCut()")
public Object around(ProceedingJoinPoint point) throws Throwable {
MethodSignature signature = (MethodSignature) point.getSignature();
Method method = signature.getMethod();
DataSource ds = method.getAnnotation(DataSource.class);
//如果未指定資料源就使用第一個資料源
if(ds == null){
DynamicDataSource.setDataSource(DataSourceNames.FIRST);
logger.debug("set datasource is " + DataSourceNames.FIRST);
}else {
DynamicDataSource.setDataSource(ds.name());
logger.debug("set datasource is " + ds.name());
}
try {
return point.proceed();
} finally {
DynamicDataSource.clearDataSource();
logger.debug("clean datasource");
}
}
@Override
public int getOrder() {
return 1;
}
}
step3：對資料源進行配置
@Configuration
public class DynamicDataSourceConfig {
@Bean
@ConfigurationProperties("spring.datasource.druid.first")
public DataSource firstDataSource(){
return DruidDataSourceBuilder.create().build();
}
@Bean
@ConfigurationProperties("spring.datasource.druid.second")
public DataSource secondDataSource(){
DataSource dataSource = DruidDataSourceBuilder.create().build();
return dataSource;
}
@Bean
@Primary
@DependsOn(value = https://www.cnblogs.com/54chensongxia/p/{"firstDataSource","secondDataSource"})
public DynamicDataSource dataSource(DataSource firstDataSource,DataSource secondDataSource) {
Map<Object, Object> targetDataSources = new HashMap<>();
targetDataSources.put(DataSourceNames.FIRST, firstDataSource);
targetDataSources.put(DataSourceNames.SECOND, secondDataSource);
return new DynamicDataSource(firstDataSource, targetDataSources);
}
}
以上就是實作雙資料源的全部配置，
使用
使用的時候非常簡單，只需要在Service層的方法上加上@DataSource注解就可以了，
@DataSource(name = DataSourceNames.SECOND)
public String selectByInfoName(String name){
//...
}
一些注意點
如果你使用了pageHelper等分頁插件，請將方言設定成自動模式， autoRuntimeDialect: true
pagehelper:
reasonable: false
supportMethodsArguments: true
params: count=countSql
autoRuntimeDialect: true
如果你使用了Druid資料源，并通過下面的形式創建資料源，要保障資料源的用戶名和密碼欄位不為null，不然DruidDataSourceWrapper這個Bean會檢測這個欄位的值，導致啟動失敗，
@Bean
@ConfigurationProperties("spring.datasource.druid.first")
public DataSource firstDataSource(){
return DruidDataSourceBuilder.create().build();
}
@Bean
@ConfigurationProperties("spring.datasource.druid.second")
public DataSource secondDataSource(){
DataSource dataSource = DruidDataSourceBuilder.create().build();
return dataSource;
}
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標籤：Java