Mybatis SqlSessionTemplate类分析

/*

 *    Copyright 2010-2012 The MyBatis Team

 *

 *    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 org.mybatis.spring;

import static java.lang.reflect.Proxy.newProxyInstance;

import static org.apache.ibatis.reflection.ExceptionUtil.unwrapThrowable;

import static org.mybatis.spring.SqlSessionUtils.closeSqlSession;

import static org.mybatis.spring.SqlSessionUtils.getSqlSession;

import static org.mybatis.spring.SqlSessionUtils.isSqlSessionTransactional;

import static org.springframework.util.Assert.notNull;

import java.lang.reflect.InvocationHandler;

import java.lang.reflect.Method;

import java.sql.Connection;

import java.util.List;

import java.util.Map;

import org.apache.ibatis.exceptions.PersistenceException;

import org.apache.ibatis.executor.BatchResult;

import org.apache.ibatis.session.Configuration;

import org.apache.ibatis.session.ExecutorType;

import org.apache.ibatis.session.ResultHandler;

import org.apache.ibatis.session.RowBounds;

import org.apache.ibatis.session.SqlSession;

import org.apache.ibatis.session.SqlSessionFactory;

import org.springframework.dao.support.PersistenceExceptionTranslator;

/**

 * Thread safe, Spring managed, {@code SqlSession} that works with Spring

 * transaction management to ensure that that the actual SqlSession used is the

 * one associated with the current Spring transaction. In addition, it manages

 * the session life-cycle, including closing, committing or rolling back the

 * session as necessary based on the Spring transaction configuration.

 * <p>

 * The template needs a SqlSessionFactory to create SqlSessions, passed as a

 * constructor argument. It also can be constructed indicating the executor type

 * to be used, if not, the default executor type, defined in the session factory

 * will be used.

 * <p>

 * This template converts MyBatis PersistenceExceptions into unchecked

 * DataAccessExceptions, using, by default, a {@code MyBatisExceptionTranslator}.

 * <p>

 * Because SqlSessionTemplate is thread safe, a single instance can be shared

 * by all DAOs; there should also be a small memory savings by doing this. This

 * pattern can be used in Spring configuration files as follows:

 *

 * <pre class="code">

 * {@code

 * <bean id="sqlSessionTemplate" class="org.mybatis.spring.SqlSessionTemplate">

 *   <constructor-arg ref="sqlSessionFactory" />

 * </bean>

 * }

 * </pre>

 *

 * @see SqlSessionFactory

 * @see MyBatisExceptionTranslator

 * @version $Id: SqlSessionTemplate.java 4898 2012-03-12 10:19:45Z simone.tripodi $

 */

public class SqlSessionTemplate implements SqlSession {

  private final SqlSessionFactory sqlSessionFactory;

  private final ExecutorType executorType;

  private final SqlSession sqlSessionProxy;

  private final PersistenceExceptionTranslator exceptionTranslator;

  /**

   * Constructs a Spring managed SqlSession with the {@code SqlSessionFactory}

   * provided as an argument.

   *

   * @param sqlSessionFactory

   */

  public SqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {

    this(sqlSessionFactory, sqlSessionFactory.getConfiguration().getDefaultExecutorType());

  }

  /**

   * Constructs a Spring managed SqlSession with the {@code SqlSessionFactory}

   * provided as an argument and the given {@code ExecutorType}

   * {@code ExecutorType} cannot be changed once the {@code SqlSessionTemplate}

   * is constructed.

   *

   * @param sqlSessionFactory

   * @param executorType

   */

  public SqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType) {

    this(sqlSessionFactory, executorType,

        new MyBatisExceptionTranslator(

            sqlSessionFactory.getConfiguration().getEnvironment().getDataSource(), true));

  }

  /**

   * Constructs a Spring managed {@code SqlSession} with the given

   * {@code SqlSessionFactory} and {@code ExecutorType}.

   * A custom {@code SQLExceptionTranslator} can be provided as an

   * argument so any {@code PersistenceException} thrown by MyBatis

   * can be custom translated to a {@code RuntimeException}

   * The {@code SQLExceptionTranslator} can also be null and thus no

   * exception translation will be done and MyBatis exceptions will be

   * thrown

   *

   * @param sqlSessionFactory

   * @param executorType

   * @param exceptionTranslator

   */

  public SqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType,

      PersistenceExceptionTranslator exceptionTranslator) {

    notNull(sqlSessionFactory, "Property ‘sqlSessionFactory‘ is required");

    notNull(executorType, "Property ‘executorType‘ is required");

    this.sqlSessionFactory = sqlSessionFactory;

    this.executorType = executorType;

    this.exceptionTranslator = exceptionTranslator;

    this.sqlSessionProxy = (SqlSession) newProxyInstance(

        SqlSessionFactory.class.getClassLoader(),

        new Class[] { SqlSession.class },

        new SqlSessionInterceptor());

  }

  public SqlSessionFactory getSqlSessionFactory() {

    return this.sqlSessionFactory;

  }

  public ExecutorType getExecutorType() {

    return this.executorType;

  }

  public PersistenceExceptionTranslator getPersistenceExceptionTranslator() {

    return this.exceptionTranslator;

  }

  /**

   * {@inheritDoc}

   */

  public <T> T selectOne(String statement) {

    return this.sqlSessionProxy.<T> selectOne(statement);

  }

  /**

   * {@inheritDoc}

   */

  public <T> T selectOne(String statement, Object parameter) {

    return this.sqlSessionProxy.<T> selectOne(statement, parameter);

  }

  /**

   * {@inheritDoc}

   */

  public <K, V> Map<K, V> selectMap(String statement, String mapKey) {

    return this.sqlSessionProxy.<K, V> selectMap(statement, mapKey);

  }

  /**

   * {@inheritDoc}

   */

  public <K, V> Map<K, V> selectMap(String statement, Object parameter, String mapKey) {

    return this.sqlSessionProxy.<K, V> selectMap(statement, parameter, mapKey);

  }

  /**

   * {@inheritDoc}

   */

  public <K, V> Map<K, V> selectMap(String statement, Object parameter, String mapKey, RowBounds rowBounds) {

    return this.sqlSessionProxy.<K, V> selectMap(statement, parameter, mapKey, rowBounds);

  }

  /**

   * {@inheritDoc}

   */

  public <E> List<E> selectList(String statement) {

    return this.sqlSessionProxy.<E> selectList(statement);

  }

  /**

   * {@inheritDoc}

   */

  public <E> List<E> selectList(String statement, Object parameter) {

    return this.sqlSessionProxy.<E> selectList(statement, parameter);

  }

  /**

   * {@inheritDoc}

   */

  public <E> List<E> selectList(String statement, Object parameter, RowBounds rowBounds) {

    return this.sqlSessionProxy.<E> selectList(statement, parameter, rowBounds);

  }

  /**

   * {@inheritDoc}

   */

  public void select(String statement, ResultHandler handler) {

    this.sqlSessionProxy.select(statement, handler);

  }

  /**

   * {@inheritDoc}

   */

  public void select(String statement, Object parameter, ResultHandler handler) {

    this.sqlSessionProxy.select(statement, parameter, handler);

  }

  /**

   * {@inheritDoc}

   */

  public void select(String statement, Object parameter, RowBounds rowBounds, ResultHandler handler) {

    this.sqlSessionProxy.select(statement, parameter, rowBounds, handler);

  }

  /**

   * {@inheritDoc}

   */

  public int insert(String statement) {

    return this.sqlSessionProxy.insert(statement);

  }

  /**

   * {@inheritDoc}

   */

  public int insert(String statement, Object parameter) {

    return this.sqlSessionProxy.insert(statement, parameter);

  }

  /**

   * {@inheritDoc}

   */

  public int update(String statement) {

    return this.sqlSessionProxy.update(statement);

  }

  /**

   * {@inheritDoc}

   */

  public int update(String statement, Object parameter) {

    return this.sqlSessionProxy.update(statement, parameter);

  }

  /**

   * {@inheritDoc}

   */

  public int delete(String statement) {

    return this.sqlSessionProxy.delete(statement);

  }

  /**

   * {@inheritDoc}

   */

  public int delete(String statement, Object parameter) {

    return this.sqlSessionProxy.delete(statement, parameter);

  }

  /**

   * {@inheritDoc}

   */

  public <T> T getMapper(Class<T> type) {

    return getConfiguration().getMapper(type, this);

  }

  /**

   * {@inheritDoc}

   */

  public void commit() {

    throw new UnsupportedOperationException("Manual commit is not allowed over a Spring managed SqlSession");

  }

  /**

   * {@inheritDoc}

   */

  public void commit(boolean force) {

    throw new UnsupportedOperationException("Manual commit is not allowed over a Spring managed SqlSession");

  }

  /**

   * {@inheritDoc}

   */

  public void rollback() {

    throw new UnsupportedOperationException("Manual rollback is not allowed over a Spring managed SqlSession");

  }

  /**

   * {@inheritDoc}

   */

  public void rollback(boolean force) {

    throw new UnsupportedOperationException("Manual rollback is not allowed over a Spring managed SqlSession");

  }

  /**

   * {@inheritDoc}

   */

  public void close() {

    throw new UnsupportedOperationException("Manual close is not allowed over a Spring managed SqlSession");

  }

  /**

   * {@inheritDoc}

   */

  public void clearCache() {

    this.sqlSessionProxy.clearCache();

  }

  /**

   * {@inheritDoc}

   *

   */

  public Configuration getConfiguration() {

    return this.sqlSessionFactory.getConfiguration();

  }

  /**

   * {@inheritDoc}

   */

  public Connection getConnection() {

    return this.sqlSessionProxy.getConnection();

  }

  /**

   * {@inheritDoc}

   *

   * @since 1.0.2

   *

   */

  public List<BatchResult> flushStatements() {

    return this.sqlSessionProxy.flushStatements();

  }

  /**

   * Proxy needed to route MyBatis method calls to the proper SqlSession got

   * from Spring‘s Transaction Manager

   * It also unwraps exceptions thrown by {@code Method#invoke(Object, Object...)} to

   * pass a {@code PersistenceException} to the {@code PersistenceExceptionTranslator}.

   */

  private class SqlSessionInterceptor implements InvocationHandler {

    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {

      final SqlSession sqlSession = getSqlSession(

          SqlSessionTemplate.this.sqlSessionFactory,

          SqlSessionTemplate.this.executorType,

          SqlSessionTemplate.this.exceptionTranslator);

      try {

        Object result = method.invoke(sqlSession, args);

        if (!isSqlSessionTransactional(sqlSession, SqlSessionTemplate.this.sqlSessionFactory)) {

          // force commit even on non-dirty sessions because some databases require

          // a commit/rollback before calling close()

          sqlSession.commit(true);

        }

        return result;

      } catch (Throwable t) {

        Throwable unwrapped = unwrapThrowable(t);

        if (SqlSessionTemplate.this.exceptionTranslator != null && unwrapped instanceof PersistenceException) {

          Throwable translated = SqlSessionTemplate.this.exceptionTranslator.translateExceptionIfPossible((PersistenceException) unwrapped);

          if (translated != null) {

            unwrapped = translated;

          }

        }

        throw unwrapped;

      } finally {

        closeSqlSession(sqlSession, SqlSessionTemplate.this.sqlSessionFactory);

      }

    }

  }

}