1 /*
2 * Copyright 2002-2012 the original author or authors.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 package org.springframework.jdbc.datasource.lookup;
18
19 import java.sql.Connection;
20 import java.sql.SQLException;
21 import java.util.HashMap;
22 import java.util.Map;
23 import javax.sql.DataSource;
24
25 import org.springframework.beans.factory.InitializingBean;
26 import org.springframework.jdbc.datasource.AbstractDataSource;
27 import org.springframework.util.Assert;
28
29 /**
30 * Abstract {@link javax.sql.DataSource} implementation that routes {@link #getConnection()}
31 * calls to one of various target DataSources based on a lookup key. The latter is usually
32 * (but not necessarily) determined through some thread-bound transaction context.
33 *
34 * @author Juergen Hoeller
35 * @since 2.0.1
36 * @see #setTargetDataSources
37 * @see #setDefaultTargetDataSource
38 * @see #determineCurrentLookupKey()
39 */
40 public abstract class AbstractRoutingDataSource extends AbstractDataSource implements InitializingBean {
41
42 private Map<Object, Object> targetDataSources;
43
44 private Object defaultTargetDataSource;
45
46 private boolean lenientFallback = true;
47
48 private DataSourceLookup dataSourceLookup = new JndiDataSourceLookup();
49
50 private Map<Object, DataSource> resolvedDataSources;
51
52 private DataSource resolvedDefaultDataSource;
53
54
55 /**
56 * Specify the map of target DataSources, with the lookup key as key.
57 * The mapped value can either be a corresponding {@link javax.sql.DataSource}
58 * instance or a data source name String (to be resolved via a
59 * {@link #setDataSourceLookup DataSourceLookup}).
60 * <p>The key can be of arbitrary type; this class implements the
61 * generic lookup process only. The concrete key representation will
62 * be handled by {@link #resolveSpecifiedLookupKey(Object)} and
63 * {@link #determineCurrentLookupKey()}.
64 */
65 public void setTargetDataSources(Map<Object, Object> targetDataSources) {
66 this.targetDataSources = targetDataSources;
67 }
68
69 /**
70 * Specify the default target DataSource, if any.
71 * <p>The mapped value can either be a corresponding {@link javax.sql.DataSource}
72 * instance or a data source name String (to be resolved via a
73 * {@link #setDataSourceLookup DataSourceLookup}).
74 * <p>This DataSource will be used as target if none of the keyed
75 * {@link #setTargetDataSources targetDataSources} match the
76 * {@link #determineCurrentLookupKey()} current lookup key.
77 */
78 public void setDefaultTargetDataSource(Object defaultTargetDataSource) {
79 this.defaultTargetDataSource = defaultTargetDataSource;
80 }
81
82 /**
83 * Specify whether to apply a lenient fallback to the default DataSource
84 * if no specific DataSource could be found for the current lookup key.
85 * <p>Default is "true", accepting lookup keys without a corresponding entry
86 * in the target DataSource map - simply falling back to the default DataSource
87 * in that case.
88 * <p>Switch this flag to "false" if you would prefer the fallback to only apply
89 * if the lookup key was {@code null}. Lookup keys without a DataSource
90 * entry will then lead to an IllegalStateException.
91 * @see #setTargetDataSources
92 * @see #setDefaultTargetDataSource
93 * @see #determineCurrentLookupKey()
94 */
95 public void setLenientFallback(boolean lenientFallback) {
96 this.lenientFallback = lenientFallback;
97 }
98
99 /**
100 * Set the DataSourceLookup implementation to use for resolving data source
101 * name Strings in the {@link #setTargetDataSources targetDataSources} map.
102 * <p>Default is a {@link JndiDataSourceLookup}, allowing the JNDI names
103 * of application server DataSources to be specified directly.
104 */
105 public void setDataSourceLookup(DataSourceLookup dataSourceLookup) {
106 this.dataSourceLookup = (dataSourceLookup != null ? dataSourceLookup : new JndiDataSourceLookup());
107 }
108
109
110 @Override
111 public void afterPropertiesSet() {
112 if (this.targetDataSources == null) {
113 throw new IllegalArgumentException("Property 'targetDataSources' is required");
114 }
115 this.resolvedDataSources = new HashMap<Object, DataSource>(this.targetDataSources.size());
116 for (Map.Entry<Object, Object> entry : this.targetDataSources.entrySet()) {
117 Object lookupKey = resolveSpecifiedLookupKey(entry.getKey());
118 DataSource dataSource = resolveSpecifiedDataSource(entry.getValue());
119 this.resolvedDataSources.put(lookupKey, dataSource);
120 }
121 if (this.defaultTargetDataSource != null) {
122 this.resolvedDefaultDataSource = resolveSpecifiedDataSource(this.defaultTargetDataSource);
123 }
124 }
125
126 /**
127 * Resolve the given lookup key object, as specified in the
128 * {@link #setTargetDataSources targetDataSources} map, into
129 * the actual lookup key to be used for matching with the
130 * {@link #determineCurrentLookupKey() current lookup key}.
131 * <p>The default implementation simply returns the given key as-is.
132 * @param lookupKey the lookup key object as specified by the user
133 * @return the lookup key as needed for matching
134 */
135 protected Object resolveSpecifiedLookupKey(Object lookupKey) {
136 return lookupKey;
137 }
138
139 /**
140 * Resolve the specified data source object into a DataSource instance.
141 * <p>The default implementation handles DataSource instances and data source
142 * names (to be resolved via a {@link #setDataSourceLookup DataSourceLookup}).
143 * @param dataSource the data source value object as specified in the
144 * {@link #setTargetDataSources targetDataSources} map
145 * @return the resolved DataSource (never {@code null})
146 * @throws IllegalArgumentException in case of an unsupported value type
147 */
148 protected DataSource resolveSpecifiedDataSource(Object dataSource) throws IllegalArgumentException {
149 if (dataSource instanceof DataSource) {
150 return (DataSource) dataSource;
151 }
152 else if (dataSource instanceof String) {
153 return this.dataSourceLookup.getDataSource((String) dataSource);
154 }
155 else {
156 throw new IllegalArgumentException(
157 "Illegal data source value - only [javax.sql.DataSource] and String supported: " + dataSource);
158 }
159 }
160
161
162 @Override
163 public Connection getConnection() throws SQLException {
164 return determineTargetDataSource().getConnection();
165 }
166
167 @Override
168 public Connection getConnection(String username, String password) throws SQLException {
169 return determineTargetDataSource().getConnection(username, password);
170 }
171
172 @Override
173 @SuppressWarnings("unchecked")
174 public <T> T unwrap(Class<T> iface) throws SQLException {
175 if (iface.isInstance(this)) {
176 return (T) this;
177 }
178 return determineTargetDataSource().unwrap(iface);
179 }
180
181 @Override
182 public boolean isWrapperFor(Class<?> iface) throws SQLException {
183 return (iface.isInstance(this) || determineTargetDataSource().isWrapperFor(iface));
184 }
185
186 /**
187 * Retrieve the current target DataSource. Determines the
188 * {@link #determineCurrentLookupKey() current lookup key}, performs
189 * a lookup in the {@link #setTargetDataSources targetDataSources} map,
190 * falls back to the specified
191 * {@link #setDefaultTargetDataSource default target DataSource} if necessary.
192 * @see #determineCurrentLookupKey()
193 */
194 protected DataSource determineTargetDataSource() {
195 Assert.notNull(this.resolvedDataSources, "DataSource router not initialized");
196 Object lookupKey = determineCurrentLookupKey();
197 DataSource dataSource = this.resolvedDataSources.get(lookupKey);
198 if (dataSource == null && (this.lenientFallback || lookupKey == null)) {
199 dataSource = this.resolvedDefaultDataSource;
200 }
201 if (dataSource == null) {
202 throw new IllegalStateException("Cannot determine target DataSource for lookup key [" + lookupKey + "]");
203 }
204 return dataSource;
205 }
206
207 /**
208 * Determine the current lookup key. This will typically be
209 * implemented to check a thread-bound transaction context.
210 * <p>Allows for arbitrary keys. The returned key needs
211 * to match the stored lookup key type, as resolved by the
212 * {@link #resolveSpecifiedLookupKey} method.
213 */
214 protected abstract Object determineCurrentLookupKey();
215
216 }