org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource-编程知识

DynamicDataSource-CSDN博客
/** Copyright 2002-2020 the original author or authors.** Licensed under the Apache License, Version 2.0 (the "License");* you may not use this file except in compliance with the License.* You may obtain a copy of the License at**      https://www.apache.org/licenses/LICENSE-2.0** Unless required by applicable law or agreed to in writing, software* distributed under the License is distributed on an "AS IS" BASIS,* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.* See the License for the specific language governing permissions and* limitations under the License.*/package org.springframework.jdbc.datasource.lookup;import java.sql.Connection;
import java.sql.SQLException;
import java.util.Collections;
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;
import org.springframework.util.CollectionUtils;/*** Abstract {@link javax.sql.DataSource} implementation that routes {@link #getConnection()}* calls to one of various target DataSources based on a lookup key. The latter is usually* (but not necessarily) determined through some thread-bound transaction context.** @author Juergen Hoeller* @since 2.0.1* @see #setTargetDataSources* @see #setDefaultTargetDataSource* @see #determineCurrentLookupKey()*/
public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean {@Nullableprivate Map<Object, Object> targetDataSources;@Nullableprivate Object defaultTargetDataSource;private boolean lenientFallback = true;private DataSourceLookup dataSourceLookup = new JndiDataSourceLookup();@Nullableprivate Map<Object, DataSource> resolvedDataSources;@Nullableprivate DataSource resolvedDefaultDataSource;/*** Specify the map of target DataSources, with the lookup key as key.* The mapped value can either be a corresponding {@link javax.sql.DataSource}* instance or a data source name String (to be resolved via a* {@link #setDataSourceLookup DataSourceLookup}).* <p>The key can be of arbitrary type; this class implements the* generic lookup process only. The concrete key representation will* be handled by {@link #resolveSpecifiedLookupKey(Object)} and* {@link #determineCurrentLookupKey()}.*/public void setTargetDataSources(Map<Object, Object> targetDataSources) {this.targetDataSources = targetDataSources;}/*** Specify the default target DataSource, if any.* <p>The mapped value can either be a corresponding {@link javax.sql.DataSource}* instance or a data source name String (to be resolved via a* {@link #setDataSourceLookup DataSourceLookup}).* <p>This DataSource will be used as target if none of the keyed* {@link #setTargetDataSources targetDataSources} match the* {@link #determineCurrentLookupKey()} current lookup key.*/public void setDefaultTargetDataSource(Object defaultTargetDataSource) {this.defaultTargetDataSource = defaultTargetDataSource;}/*** Specify whether to apply a lenient fallback to the default DataSource* if no specific DataSource could be found for the current lookup key.* <p>Default is "true", accepting lookup keys without a corresponding entry* in the target DataSource map - simply falling back to the default DataSource* in that case.* <p>Switch this flag to "false" if you would prefer the fallback to only apply* if the lookup key was {@code null}. Lookup keys without a DataSource* entry will then lead to an IllegalStateException.* @see #setTargetDataSources* @see #setDefaultTargetDataSource* @see #determineCurrentLookupKey()*/public void setLenientFallback(boolean lenientFallback) {this.lenientFallback = lenientFallback;}/*** Set the DataSourceLookup implementation to use for resolving data source* name Strings in the {@link #setTargetDataSources targetDataSources} map.* <p>Default is a {@link JndiDataSourceLookup}, allowing the JNDI names* of application server DataSources to be specified directly.*/public void setDataSourceLookup(@Nullable DataSourceLookup dataSourceLookup) {this.dataSourceLookup = (dataSourceLookup != null ? dataSourceLookup : new JndiDataSourceLookup());}@Overridepublic void afterPropertiesSet() {if (this.targetDataSources == null) {throw new IllegalArgumentException("Property 'targetDataSources' is required");}this.resolvedDataSources = CollectionUtils.newHashMap(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);}}/*** Resolve the given lookup key object, as specified in the* {@link #setTargetDataSources targetDataSources} map, into* the actual lookup key to be used for matching with the* {@link #determineCurrentLookupKey() current lookup key}.* <p>The default implementation simply returns the given key as-is.* @param lookupKey the lookup key object as specified by the user* @return the lookup key as needed for matching*/protected Object resolveSpecifiedLookupKey(Object lookupKey) {return lookupKey;}/*** Resolve the specified data source object into a DataSource instance.* <p>The default implementation handles DataSource instances and data source* names (to be resolved via a {@link #setDataSourceLookup DataSourceLookup}).* @param dataSource the data source value object as specified in the* {@link #setTargetDataSources targetDataSources} map* @return the resolved DataSource (never {@code null})* @throws IllegalArgumentException in case of an unsupported value type*/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);}}/*** Return the resolved target DataSources that this router manages.* @return an unmodifiable map of resolved lookup keys and DataSources* @throws IllegalStateException if the target DataSources are not resolved yet* @since 5.2.9* @see #setTargetDataSources*/public Map<Object, DataSource> getResolvedDataSources() {Assert.state(this.resolvedDataSources != null, "DataSources not resolved yet - call afterPropertiesSet");return Collections.unmodifiableMap(this.resolvedDataSources);}/*** Return the resolved default target DataSource, if any.* @return the default DataSource, or {@code null} if none or not resolved yet* @since 5.2.9* @see #setDefaultTargetDataSource*/@Nullablepublic DataSource getResolvedDefaultDataSource() {return this.resolvedDefaultDataSource;}@Overridepublic Connection getConnection() throws SQLException {return determineTargetDataSource().getConnection();}@Overridepublic 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);}@Overridepublic boolean isWrapperFor(Class<?> iface) throws SQLException {return (iface.isInstance(this) || determineTargetDataSource().isWrapperFor(iface));}/*** Retrieve the current target DataSource. Determines the* {@link #determineCurrentLookupKey() current lookup key}, performs* a lookup in the {@link #setTargetDataSources targetDataSources} map,* falls back to the specified* {@link #setDefaultTargetDataSource default target DataSource} if necessary.* @see #determineCurrentLookupKey()*/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;}/*** Determine the current lookup key. This will typically be* implemented to check a thread-bound transaction context.* <p>Allows for arbitrary keys. The returned key needs* to match the stored lookup key type, as resolved by the* {@link #resolveSpecifiedLookupKey} method.*/@Nullableprotected abstract Object determineCurrentLookupKey();}
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