com._4dconcept.springframework.data.marklogic.datasource.lookup.IsolationLevelContentSourceRouter.java Source code

Introduction

Here is the source code for com._4dconcept.springframework.data.marklogic.datasource.lookup.IsolationLevelContentSourceRouter.java

Source

/*
 * Copyright 2017 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
 *
 *      http://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 com._4dconcept.springframework.data.marklogic.datasource.lookup;

import org.springframework.core.Constants;
import org.springframework.lang.Nullable;
import org.springframework.transaction.TransactionDefinition;
import org.springframework.transaction.support.DefaultTransactionDefinition;
import org.springframework.transaction.support.TransactionSynchronizationManager;

/**
 * ContentSource that routes to one of various target ContentSources based on the
 * current transaction isolation level. The target ContentSources need to be
 * configured with the isolation level name as key, as defined on the
 * {@link TransactionDefinition TransactionDefinition interface}.
 *
 * <p>This is particularly useful in combination with JTA transaction management
 * (typically through Spring's {@link org.springframework.transaction.jta.JtaTransactionManager}).
 * Standard JTA does not support transaction-specific isolation levels. Some JTA
 * providers support isolation levels as a vendor-specific extension (e.g. WebLogic),
 * which is the preferred way of addressing this. As alternative (e.g. on WebSphere),
 * the target database can be represented through multiple JNDI ContentSources, each
 * configured with a different isolation level (for the entire ContentSource).
 * The present ContentSource router allows to transparently switch to the
 * appropriate ContentSource based on the current transaction's isolation level.
 *
 * <p>The configuration can for example look like this, assuming that the target
 * ContentSources are defined as individual Spring beans with names
 * "myRepeatableReadContentSource", "mySerializableContentSource" and "myDefaultContentSource":
 *
 * <pre class="code">
 * &lt;bean id="contentSourceRouter" class="com._4dconcept.contentfactory.extra.datasource.lookup.IsolationLevelContentSourceRouter"&gt;
 *   &lt;property name="targetContentSources"&gt;
 *     &lt;map&gt;
 *       &lt;entry key="ISOLATION_REPEATABLE_READ" value-ref="myRepeatableReadContentSource"/&gt;
 *       &lt;entry key="ISOLATION_SERIALIZABLE" value-ref="mySerializableContentSource"/&gt;
 *     &lt;/map&gt;
 *   &lt;/property&gt;
 *   &lt;property name="defaultTargetContentSource" ref="myDefaultContentSource"/&gt;
 * &lt;/bean&gt;</pre>
 *
 * Note: If you are using this router in combination with Spring's
 * {@link org.springframework.transaction.jta.JtaTransactionManager},
 * don't forget to switch the "allowCustomIsolationLevels" flag to "true".
 * (By default, JtaTransactionManager will only accept a default isolation level
 * because of the lack of isolation level support in standard JTA itself.)
 *
 * <pre class="code">
 * &lt;bean id="transactionManager" class="org.springframework.transaction.jta.JtaTransactionManager"&gt;
 *   &lt;property name="allowCustomIsolationLevels" value="true"/&gt;
 * &lt;/bean&gt;</pre>
 *
 * @author Stphane Toussaint
 * @author Juergen Hoeller
 *
 * @see #setTargetContentSources
 * @see #setDefaultTargetContentSource
 * @see TransactionDefinition#ISOLATION_READ_UNCOMMITTED
 * @see TransactionDefinition#ISOLATION_READ_COMMITTED
 * @see TransactionDefinition#ISOLATION_REPEATABLE_READ
 * @see TransactionDefinition#ISOLATION_SERIALIZABLE
 * @see org.springframework.transaction.jta.JtaTransactionManager
 */
public class IsolationLevelContentSourceRouter extends AbstractRoutingContentSource {

    /** Constants instance for TransactionDefinition */
    private static final Constants constants = new Constants(TransactionDefinition.class);

    /**
     * Supports Integer values for the isolation level constants
     * as well as isolation level names as defined on the
     * {@link TransactionDefinition TransactionDefinition interface}.
     */
    @Override
    protected Object resolveSpecifiedLookupKey(Object lookupKey) {
        if (lookupKey instanceof Integer) {
            return lookupKey;
        } else if (lookupKey instanceof String) {
            String constantName = (String) lookupKey;
            if (!constantName.startsWith(DefaultTransactionDefinition.PREFIX_ISOLATION)) {
                throw new IllegalArgumentException("Only isolation constants allowed");
            }
            return constants.asNumber(constantName);
        } else {
            throw new IllegalArgumentException(
                    "Invalid lookup key - needs to be isolation level Integer or isolation level name String: "
                            + lookupKey);
        }
    }

    @Override
    @Nullable
    protected Object determineCurrentLookupKey() {
        return TransactionSynchronizationManager.getCurrentTransactionIsolationLevel();
    }

}