设计模式课程 设计模式精讲 6-3 抽象工厂源码解析

1　　　　源码解析

1.1　　连接源码解析

1.2　　mybaties 的sqlsession源码解析

1　　　　源码解析

1.1　　连接源码解析

Connection.java(两个方法属于同一个产品族，这是连接的父类)

mysql获取的是同一产品族下的statement和同一产品族下的preparestatement

oracle也是

Statement createStatement() throws SQLException;

    /**
     * Creates a <code>PreparedStatement</code> object for sending
     * parameterized SQL statements to the database.
     * <P>
     * A SQL statement with or without IN parameters can be
     * pre-compiled and stored in a <code>PreparedStatement</code> object. This
     * object can then be used to efficiently execute this statement
     * multiple times.
     *
     * <P><B>Note:</B> This method is optimized for handling
     * parametric SQL statements that benefit from precompilation. If
     * the driver supports precompilation,
     * the method <code>prepareStatement</code> will send
     * the statement to the database for precompilation. Some drivers
     * may not support precompilation. In this case, the statement may
     * not be sent to the database until the <code>PreparedStatement</code>
     * object is executed.  This has no direct effect on users; however, it does
     * affect which methods throw certain <code>SQLException</code> objects.
     * <P>
     * Result sets created using the returned <code>PreparedStatement</code>
     * object will by default be type <code>TYPE_FORWARD_ONLY</code>
     * and have a concurrency level of <code>CONCUR_READ_ONLY</code>.
     * The holdability of the created result sets can be determined by
     * calling {@link #getHoldability}.
     *
     * @param sql an SQL statement that may contain one or more '?' IN
     * parameter placeholders
     * @return a new default <code>PreparedStatement</code> object containing the
     * pre-compiled SQL statement
     * @exception SQLException if a database access error occurs
     * or this method is called on a closed connection
     */
    PreparedStatement prepareStatement(String sql)
        throws SQLException;

    /**
     * Creates a <code>CallableStatement</code> object for calling
     * database stored procedures.
     * The <code>CallableStatement</code> object provides
     * methods for setting up its IN and OUT parameters, and
     * methods for executing the call to a stored procedure.
     *
     * <P><B>Note:</B> This method is optimized for handling stored
     * procedure call statements. Some drivers may send the call
     * statement to the database when the method <code>prepareCall</code>
     * is done; others
     * may wait until the <code>CallableStatement</code> object
     * is executed. This has no
     * direct effect on users; however, it does affect which method
     * throws certain SQLExceptions.
     * <P>
     * Result sets created using the returned <code>CallableStatement</code>
     * object will by default be type <code>TYPE_FORWARD_ONLY</code>
     * and have a concurrency level of <code>CONCUR_READ_ONLY</code>.
     * The holdability of the created result sets can be determined by
     * calling {@link #getHoldability}.
     *
     * @param sql an SQL statement that may contain one or more '?'
     * parameter placeholders. Typically this statement is specified using JDBC
     * call escape syntax.
     * @return a new default <code>CallableStatement</code> object containing the
     * pre-compiled SQL statement
     * @exception SQLException if a database access error occurs
     * or this method is called on a closed connection
     */

Statement.java(executeQuery方法和executeUpdate方法属于同一个产品族)

ResultSet executeQuery(String sql) throws SQLException;

    /**
     * Executes the given SQL statement, which may be an <code>INSERT</code>,
     * <code>UPDATE</code>, or <code>DELETE</code> statement or an
     * SQL statement that returns nothing, such as an SQL DDL statement.
     *<p>
     * <strong>Note:</strong>This method cannot be called on a
     * <code>PreparedStatement</code> or <code>CallableStatement</code>.
     * @param sql an SQL Data Manipulation Language (DML) statement, such as <code>INSERT</code>, <code>UPDATE</code> or
     * <code>DELETE</code>; or an SQL statement that returns nothing,
     * such as a DDL statement.
     *
     * @return either (1) the row count for SQL Data Manipulation Language (DML) statements
     *         or (2) 0 for SQL statements that return nothing
     *
     * @exception SQLException if a database access error occurs,
     * this method is called on a closed <code>Statement</code>, the given
     * SQL statement produces a <code>ResultSet</code> object, the method is called on a
     * <code>PreparedStatement</code> or <code>CallableStatement</code>
     * @throws SQLTimeoutException when the driver has determined that the
     * timeout value that was specified by the {@code setQueryTimeout}
     * method has been exceeded and has at least attempted to cancel
     * the currently running {@code Statement}
     */
    int executeUpdate(String sql) throws SQLException;

    /**
     * Releases this <code>Statement</code> object's database
     * and JDBC resources immediately instead of waiting for
     * this to happen when it is automatically closed.
     * It is generally good practice to release resources as soon as
     * you are finished with them to avoid tying up database
     * resources.
     * <P>
     * Calling the method <code>close</code> on a <code>Statement</code>
     * object that is already closed has no effect.
     * <P>
     * <B>Note:</B>When a <code>Statement</code> object is
     * closed, its current <code>ResultSet</code> object, if one exists, is
     * also closed.
     *
     * @exception SQLException if a database access error occurs
     */

1.2　　mybaties 的sqlsession源码解析

sqlsessionfactory：

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package org.apache.ibatis.session;

import java.sql.Connection;

public interface SqlSessionFactory {
    SqlSession openSession();

    SqlSession openSession(boolean var1);

    SqlSession openSession(Connection var1);

    SqlSession openSession(TransactionIsolationLevel var1);

    SqlSession openSession(ExecutorType var1);

    SqlSession openSession(ExecutorType var1, boolean var2);

    SqlSession openSession(ExecutorType var1, TransactionIsolationLevel var2);

    SqlSession openSession(ExecutorType var1, Connection var2);

    Configuration getConfiguration();
}

子类1：SqlSessionManager

 public Configuration getConfiguration() {
        return this.sqlSessionFactory.getConfiguration();
    }

    public SqlSession openSession(ExecutorType execType, TransactionIsolationLevel level) {
        return this.sqlSessionFactory.openSession(execType, level);
    }

子类2：

    public Configuration getConfiguration() {
        return this.configuration;
    }

 public SqlSession openSession(ExecutorType execType, TransactionIsolationLevel level) {
        return this.openSessionFromDataSource(execType, level, false);
    }

    private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) {
        Transaction tx = null;

        DefaultSqlSession var8;
        try {
            Environment environment = this.configuration.getEnvironment();　　　　　　　　　　　　　　　　　　　　//获取环境变量
            TransactionFactory transactionFactory = this.getTransactionFactoryFromEnvironment(environment); 　//初始化事务工厂
            tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);　　　　//通过工厂获得事务对象
            Executor executor = this.configuration.newExecutor(tx, execType);　　　　　　　　　　　　　　　　//通过事务入参获取执行器
            var8 = new DefaultSqlSession(this.configuration, executor, autoCommit);　　　　　　　　　　　　 //返回defaultsqlsession
        } catch (Exception var12) {
            this.closeTransaction(tx);
            throw ExceptionFactory.wrapException("Error opening session.  Cause: " + var12, var12);
        } finally {
            ErrorContext.instance().reset();
        }