• 手撸mybatis07: SQL执行器的定义和实现

    串台了06还没看,不小心先看了07 不过问题不大,06讲的是数据源池化,也是挺重要的,下次再补上.

    之前的05中,先是简单的实现了selectOne,把数据源连接查询什么的都写在里面了,那就没办法复用了,所以这一章就把那些可重复利用的代码择出来.

    Executor

    将这些查询数据库常用的步骤整合起来,后面再慢慢补充其他

    package com.linnine.mybatis.executor;

    
	/**
	 * sql执行器 接口
	 * @author linnine09
	 * @create 2022/8/3 10:48
	 */
	public interface Executor {
	
	    ResultHandler NO_RESULT_HANDLER = null;
	
	    /**
	     * 默认查询
	     * @param ms
	     * @param parameter
	     * @param resultHandler
	     * @param boundSql
	     * @param 
	     * @return
	     */
	    <E> List<E> query(MappedStatement ms, Object parameter, ResultHandler resultHandler, BoundSql boundSql);
	
	    /**
	     * 获取事务
	     * @return
	     */
	    Transaction getTransaction();
	
	    /**
	     * 提交事务
	     * @param required
	     * @throws SQLException
	     */
	    void commit(boolean required) throws SQLException;
	
	    /**
	     * 回滚
	     * @param required
	     * @throws SQLException
	     */
	    void rollback(boolean required) throws SQLException;
	
	
	    /**
	     * 关闭事务
	     * @param forceRollback
	     */
	    void close(boolean forceRollback) throws SQLException;
	
	}


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    BaseExecutor

    将一些通用的过程在这个基类抽象类中实现
    package com.linnine.mybatis.executor;

    
/**
 * 执行器 抽象基类
 * @author linnine09
 * @create 2022/8/3 11:00
 */
public abstract class BaseExecutor implements Executor{

    protected Configuration configuration;

    protected Transaction transaction;

    protected Executor wrapper;

    private boolean closed;

    public BaseExecutor(Configuration configuration, Transaction transaction) {
        this.configuration = configuration;
        this.transaction = transaction;
        this.wrapper=this;
    }

    @Override
    public <E> List<E> query(MappedStatement ms, Object parameter, ResultHandler resultHandler, BoundSql boundSql){
        if (closed){
            throw new RuntimeException("Executor was closed.");
        }
        return doQuery(ms,parameter,resultHandler,boundSql);
    }

    protected abstract  <E> List<E> doQuery(MappedStatement ms, Object parameter, ResultHandler resultHandler, BoundSql boundSql);

    @Override
    public void commit(boolean required) throws SQLException {
        if (closed){
            throw new RuntimeException("Executor was closed.");
        }
        if (required){
            transaction.commit();
        }
    }
    @Override
    public Transaction getTransaction() {
        return this.transaction;
    }

    @Override
    public void rollback(boolean required) throws SQLException {
        if (closed){
            throw new RuntimeException("Executor was closed.");
        }
        if (required){
            transaction.rollback();
        }
    }

    @Override
    public void close(boolean forceRollback) throws SQLException {
        if (closed){
            throw new RuntimeException("Executor was closed.");
        }
        if (forceRollback){
            transaction.close();
        }
    }
}


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    SimpleExecutor

    整合基本的查询步骤

    package com.linnine.mybatis.executor;

    
/**
 * @author linnine09
 * @create 2022/8/3 11:10
 */
public class SimpleExecutor extends BaseExecutor{

    public SimpleExecutor(Configuration configuration, Transaction transaction) {
        super(configuration, transaction);
    }

    @Override
    protected <E> List<E> doQuery(MappedStatement ms, Object parameter, ResultHandler resultHandler, BoundSql boundSql) {
        Configuration configuration = ms.getConfiguration();
        //这个类在下面
        StatementHandler handler = configuration.newStatementHandler(this, ms, parameter, resultHandler, boundSql);
        try {
            Connection connection = transaction.getConnection();
            Statement statement = handler.prepare(connection);
            handler.parameterize(statement);
            return handler.query(statement,resultHandler);
        } catch (SQLException e) {
            e.printStackTrace();
            return null;
        }

    }


}


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    StatementHandler

    处理一下sql语句

    package com.linnine.mybatis.executor.statement;

    

/**
 * 语句处理器
 * @author linnine09
 * @create 2022/8/3 11:27
 */
public interface StatementHandler {

    /**
     * 准备语句
     * @param connection
     * @return
     * @throws SQLException
     */
    Statement prepare(Connection connection) throws SQLException;

    /**
     * 参数化
     * @param statement
     * @throws SQLException
     */
    void parameterize(Statement statement) throws SQLException;

    /**
     * 执行查询
     * @param statement
     * @param resultHandler
     * @param 
     * @return
     * @throws SQLException
     */
    <E> List<E> query(Statement statement, ResultHandler resultHandler) throws SQLException;

}


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    BaseStatementHandler

    还是一个基类抽象类 实现一些通用的

    package com.linnine.mybatis.executor.statement;

    /**
 * 语句处理 基础抽象类
 * @author linnine09
 * @create 2022/8/3 11:33
 */
public abstract class BaseStatementHandler implements StatementHandler {

    protected final Configuration configuration;

    protected final Executor executor;

    protected final MappedStatement mappedStatement;

    protected final Object parameterObject;

    protected final ResultSetHandler resultSetHandler;

    protected BoundSql boundSql;

    public BaseStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, ResultHandler resultHandler, BoundSql boundSql) {
        this.configuration = mappedStatement.getConfiguration();
        this.executor = executor;
        this.mappedStatement = mappedStatement;
        this.parameterObject = parameterObject;
        this.resultSetHandler = configuration.newResultSetHandler(executor,mappedStatement,boundSql);
        this.boundSql = boundSql;
    }
    @Override
    public Statement prepare(Connection connection) throws SQLException {
        Statement statement = instantiateStatement(connection);
        //设置超时时间
        statement.setQueryTimeout(350);
        statement.setFetchSize(10000);
        return statement;
    }


    /**
     * 实例化
     * @param connection
     * @return
     * @throws SQLException
     */
    protected abstract Statement instantiateStatement(Connection connection) throws  SQLException;
}


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    PreparedStatementHandler

    补充一些预处理的实现细节

    package com.linnine.mybatis.executor.statement;

    /**
 * 语句预处理类
 * @author linnine09
 * @create 2022/8/3 11:41
 */
public class PreparedStatementHandler extends BaseStatementHandler{
    public PreparedStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, ResultHandler resultHandler, BoundSql boundSql) {
        super(executor, mappedStatement, parameterObject, resultHandler, boundSql);
    }

    @Override
    protected Statement instantiateStatement(Connection connection) throws SQLException {
        String sql = boundSql.getSql();
        return connection.prepareStatement(sql);
    }

    @Override
    public void parameterize(Statement statement) throws SQLException {
        PreparedStatement ps = (PreparedStatement) statement;
        ps.setLong(1, Long.parseLong(((Object[]) parameterObject)[0].toString()));
    }

    @Override
    public <E> List<E> query(Statement statement, ResultHandler resultHandler) throws SQLException {
        PreparedStatement ps = (PreparedStatement) statement;
        ps.execute();
        return resultSetHandler.handleResultSets(ps);
    }
}


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    ResultSetHandler

    将结果集映射成出参类集合

    package com.linnine.mybatis.executor.reultset;

    /**
 * @author linnine09
 * @create 2022/8/3 11:23
 */
public interface ResultSetHandler {

    /**
     * 将结果集映射成出参类集合
     * @param statement
     * @param 
     * @return
     * @throws SQLException
     */
    <E> List<E> handleResultSets(Statement statement) throws SQLException;
}


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    ResultHandler

    暂时没看到干嘛用的

    package com.linnine.mybatis.session;

    
/**
 * 结果处理器
 * @author linnine09
 * @create 2022/8/3 11:36
 */
public interface ResultHandler {

    void handleResult();

}


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    DefaultResultSetHandler

    处理结果集的实现类 从DefaultSqlSession那边搬过来的

    package com.linnine.mybatis.executor.reultset;

    
/**
 * 处理结果集
 * @author linnine09
 * @create 2022/8/3 11:55
 */
public class DefaultResultSetHandler implements ResultSetHandler{
    private final BoundSql boundSql;

    public DefaultResultSetHandler(Executor executor, MappedStatement mappedStatement, BoundSql boundSql) {
        this.boundSql = boundSql;
    }

    /**
     * 将返回的结果映射成对象
     * @param statement
     * @param 
     * @return
     * @throws SQLException
     */
    @Override
    public <E> List<E> handleResultSets(Statement statement) throws SQLException {
        ResultSet resultSet = statement.getResultSet();
        try {
           return resultSet2Obj(resultSet,Class.forName(boundSql.getResultType()));
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
            return null;
        }
    }

    private <T> List<T> resultSet2Obj(ResultSet resultSet, Class<?> clazz) {
        List<T> list = new ArrayList<>();
        try {
            ResultSetMetaData metaData = resultSet.getMetaData();
            int columnCount = metaData.getColumnCount();
            while (resultSet.next()){
                T obj = (T) clazz.newInstance();
                for (int i = 1; i < columnCount; i++) {
                    Object value = resultSet.getObject(i);
                    String columnName = metaData.getColumnName(i);
                    String setMethod ="set"+columnName.substring(0,1).toUpperCase()+ columnName.substring(1);
                    Method method;
                    if (value instanceof Timestamp){
                        method = clazz.getMethod(setMethod, Date.class);
                    }else {
                        method = clazz.getMethod(setMethod,value.getClass());
                    }
                    method.invoke(obj,value);
                }
                list.add(obj);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return list;
    }
}


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    DefaultSqlSession

    这下里面就少了很多东西了,直接加入一个执行器,执行一下就好了

    在这里插入图片描述

    DefaultSqlSessionFactory

    这里主要通过配置去获取一个执行器

    package com.linnine.mybatis.session;

    
/**
 * @author linnine09
 */
public class DefaultSqlSessionFactory implements SqlSessionFactory{

    private Configuration configuration;

    public DefaultSqlSessionFactory(Configuration configuration) {
        this.configuration =configuration;
    }

    @Override
    public SqlSession openSqlSession() {
        final Environment environment = configuration.getEnvironment();
        TransactionFactory transactionFactory = environment.getTransactionFactory();
        Transaction tx=transactionFactory.newTransaction(environment.getDataSource(),TransactionIsolationLevel.READ_COMMITTED,false);
        Executor executor = configuration.newExecutor(tx);
        return new DefaultSqlSession(configuration,executor);
    }
}


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    Configuration

    补充了获取三个实现类的方法

    package com.linnine.mybatis.session;

        public StatementHandler newStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameter, ResultHandler resultHandler, BoundSql boundSql){
        return new PreparedStatementHandler(executor,mappedStatement,parameter,resultHandler,boundSql);
    }

    public ResultSetHandler newResultSetHandler(Executor executor, MappedStatement mappedStatement, BoundSql boundSql) {
        return new DefaultResultSetHandler(executor,mappedStatement,boundSql);
    }

    public Executor newExecutor(Transaction tx) {
        return new SimpleExecutor(this,tx);
    }

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    测试类还是上次05那个测试类 ,运行没什么大毛病

    在这里插入图片描述

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  • 原文地址：https://blog.csdn.net/weixin_45369440/article/details/126140494