wordpress互动主题,合肥建站优化,wordpress 帮助手册,有域名就可以做网站么转载自 mybatis源码阅读(六) ---StatementHandler了解一下
StatementHandler类结构图与接口设计 BaseStatementHandler#xff1a;一个抽象类#xff0c;只是实现了一些不涉及具体操作的方法
RoutingStatementHandler#xff1a;类似路由器#xff0c;根据配置文件来路由…转载自 mybatis源码阅读(六) ---StatementHandler了解一下
StatementHandler类结构图与接口设计 BaseStatementHandler一个抽象类只是实现了一些不涉及具体操作的方法
RoutingStatementHandler类似路由器根据配置文件来路由选择具体实现类SimpleStatementHandler、CallableStatementHandler和PreparedStatementHandler
SimpleStatementHandler就是直接使用普通的Statement对象这样每次执行SQL语句都需要数据库对SQL进行预编译
PrepareStatementHandler使用PrepareStatement执行虽然初次创建PrepareStatement时开销比较大但在多次处理SQL时只需要初始化一次可以有效提高性能
CallableStatementHandler使用CallableStatement执行CallableStatement是用来执行存储过程的。
在每个mapper节点可以设置statementType决定是否使用谁 如下
!-- statementType 可选配置默认配置为PREPAREDSTATEMENTPREPARED 或 CALLABLE 的一个。这会让 MyBatis 分别使用 StatementPreparedStatement 或 CallableStatement默认值PREPARED。 --
select idfindUserById resultTypecom.lpf.entity.User statementTypePREPAREDselect * from m_user where id #{id}
/select
1. StatementHandler
public interface StatementHandler {// 从连接中获取一个Statement对象Statement prepare(Connection connection, Integer transactionTimeout)throws SQLException;// 绑定Statement执行是所需要的参数void parameterize(Statement statement)throws SQLException;// 批量执行SQLvoid batch(Statement statement)throws SQLException;// 执行updatedeleteinsert语句int update(Statement statement)throws SQLException;// 执行select语句E ListE query(Statement statement, ResultHandler resultHandler)throws SQLException;E CursorE queryCursor(Statement statement)throws SQLException;BoundSql getBoundSql();// 获取封装的ParameterterHandler对象ParameterHandler getParameterHandler();}
2. BaseStatementHandler
BaseStatementHandler是一个抽象类和Executor一样使用了模板设计方法。代码如下
public abstract class BaseStatementHandler implements StatementHandler {protected final Configuration configuration;protected final ObjectFactory objectFactory;protected final TypeHandlerRegistry typeHandlerRegistry;//将结果映射成结果对象protected final ResultSetHandler resultSetHandler;// 使用传入的实参替换SQL语句中的protected final ParameterHandler parameterHandler;// 记录执行sql的executorprotected final Executor executor;protected final MappedStatement mappedStatement;// 分页用到protected final RowBounds rowBounds;protected BoundSql boundSql;protected BaseStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {this.configuration mappedStatement.getConfiguration();this.executor executor;this.mappedStatement mappedStatement;this.rowBounds rowBounds;this.typeHandlerRegistry configuration.getTypeHandlerRegistry();this.objectFactory configuration.getObjectFactory();if (boundSql null) { // issue #435, get the key before calculating the statement// 获取主键generateKeys(parameterObject);boundSql mappedStatement.getBoundSql(parameterObject);}this.boundSql boundSql;this.parameterHandler configuration.newParameterHandler(mappedStatement, parameterObject, boundSql);this.resultSetHandler configuration.newResultSetHandler(executor, mappedStatement, rowBounds, parameterHandler, resultHandler, boundSql);}Overridepublic BoundSql getBoundSql() {return boundSql;}Overridepublic ParameterHandler getParameterHandler() {return parameterHandler;}Overridepublic Statement prepare(Connection connection, Integer transactionTimeout) throws SQLException {ErrorContext.instance().sql(boundSql.getSql());Statement statement null;try {// 初始化Statement对象 instantiateStatement由具体的子类对象实现statement instantiateStatement(connection);// 设置超时时间setStatementTimeout(statement, transactionTimeout);setFetchSize(statement);return statement;} catch (SQLException e) {closeStatement(statement);throw e;} catch (Exception e) {closeStatement(statement);throw new ExecutorException(Error preparing statement. Cause: e, e);}}protected abstract Statement instantiateStatement(Connection connection) throws SQLException;protected void setStatementTimeout(Statement stmt, Integer transactionTimeout) throws SQLException {Integer queryTimeout null;if (mappedStatement.getTimeout() ! null) {queryTimeout mappedStatement.getTimeout();} else if (configuration.getDefaultStatementTimeout() ! null) {queryTimeout configuration.getDefaultStatementTimeout();}if (queryTimeout ! null) {stmt.setQueryTimeout(queryTimeout);}StatementUtil.applyTransactionTimeout(stmt, queryTimeout, transactionTimeout);}protected void setFetchSize(Statement stmt) throws SQLException {Integer fetchSize mappedStatement.getFetchSize();if (fetchSize ! null) {stmt.setFetchSize(fetchSize);return;}Integer defaultFetchSize configuration.getDefaultFetchSize();if (defaultFetchSize ! null) {stmt.setFetchSize(defaultFetchSize);}}protected void closeStatement(Statement statement) {try {if (statement ! null) {statement.close();}} catch (SQLException e) {//ignore}}protected void generateKeys(Object parameter) {KeyGenerator keyGenerator mappedStatement.getKeyGenerator();ErrorContext.instance().store();keyGenerator.processBefore(executor, mappedStatement, null, parameter);ErrorContext.instance().recall();}}
2.1 ParameterHandler
在BaseStatementHandler中有一个对象叫ParameterHandler是用来设置参数规则的当StatementHandler调用prepare方法之后接下来就是调用它来进行设置参数。
public interface ParameterHandler {Object getParameterObject();void setParameters(PreparedStatement ps)throws SQLException;}
getParameterObject是用来获取参数的setParameters(PreparedStatement ps)是用来设置参数的相当于对sql中所有的参数都执行ps.setXXX(value);
ParameterHandler的默认实现类是DefaultParameterHandler其实现了接口中定义的两个方法。
getParameterObject是获取参数这个参数值就是你传递进来的值可能是个实体、map或单个基本类型数据。
Override
public void setParameters(PreparedStatement ps) {ErrorContext.instance().activity(setting parameters).object(mappedStatement.getParameterMap().getId());// 去除SQL中的参数映射列表ListParameterMapping parameterMappings boundSql.getParameterMappings();if (parameterMappings ! null) {for (int i 0; i parameterMappings.size(); i) {ParameterMapping parameterMapping parameterMappings.get(i);if (parameterMapping.getMode() ! ParameterMode.OUT) {//过滤掉存储过程中的输出参数Object value;//记录绑定的实参值// 获取参数名称String propertyName parameterMapping.getProperty();if (boundSql.hasAdditionalParameter(propertyName)) { // issue #448 ask first for additional params//获取参数值value boundSql.getAdditionalParameter(propertyName);} else if (parameterObject null) {value null;} else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {//如果是单个值则直接赋值value parameterObject;} else {// 获取对象中相应的属性值或查找map对象中的值MetaObject metaObject configuration.newMetaObject(parameterObject);value metaObject.getValue(propertyName);}//获取参数值对应的jdbc类型TypeHandler typeHandler parameterMapping.getTypeHandler();JdbcType jdbcType parameterMapping.getJdbcType();if (value null jdbcType null) {jdbcType configuration.getJdbcTypeForNull();}try {//设置参数值和jdbc类型的对应关系typeHandler.setParameter(ps, i 1, value, jdbcType);} catch (TypeException e) {throw new TypeException(Could not set parameters for mapping: parameterMapping . Cause: e, e);} catch (SQLException e) {throw new TypeException(Could not set parameters for mapping: parameterMapping . Cause: e, e);}}}}
}
3. RoutingStatementHandler
/*** RoutingStatementHandler的主要功能就是根据mapper文件中的Statement的配置生成一个对应的StatementHandler* 可以是 SimpleStatementHandlerPreparedStatementHandlerCallableStatementHandler* 此类中的所有方法都是通过调用delegate对象的对应方法实现的*/
public class RoutingStatementHandler implements StatementHandler {private final StatementHandler delegate;public RoutingStatementHandler(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {switch (ms.getStatementType()) {case STATEMENT:delegate new SimpleStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);break;case PREPARED:delegate new PreparedStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);break;case CALLABLE:delegate new CallableStatementHandler(executor, ms, parameter, rowBounds, resultHandler, boundSql);break;default:throw new ExecutorException(Unknown statement type: ms.getStatementType());}}
}
4. SimpleStatementHandler
SimpleStatementHandler就是使用基本的Statement来执行query、batch、update等操作其实现还是比较简单的SQL语句中是没有占位符的所以相应 的paramterize()方法是空实现。
public class SimpleStatementHandler extends BaseStatementHandler {public SimpleStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {super(executor, mappedStatement, parameter, rowBounds, resultHandler, boundSql);}Overridepublic int update(Statement statement) throws SQLException {String sql boundSql.getSql();Object parameterObject boundSql.getParameterObject();KeyGenerator keyGenerator mappedStatement.getKeyGenerator();int rows;if (keyGenerator instanceof Jdbc3KeyGenerator) {// 生成主键statement.execute(sql, Statement.RETURN_GENERATED_KEYS);rows statement.getUpdateCount();keyGenerator.processAfter(executor, mappedStatement, statement, parameterObject);} else if (keyGenerator instanceof SelectKeyGenerator) {statement.execute(sql);rows statement.getUpdateCount();// 生成主键 keyGenerator.processAfter(executor, mappedStatement, statement, parameterObject);} else {statement.execute(sql);rows statement.getUpdateCount();}return rows;}Overridepublic void batch(Statement statement) throws SQLException {String sql boundSql.getSql();statement.addBatch(sql);}Overridepublic E ListE query(Statement statement, ResultHandler resultHandler) throws SQLException {String sql boundSql.getSql();statement.execute(sql);return resultSetHandler.EhandleResultSets(statement);}Overridepublic E CursorE queryCursor(Statement statement) throws SQLException {String sql boundSql.getSql();statement.execute(sql);return resultSetHandler.EhandleCursorResultSets(statement);}Overrideprotected Statement instantiateStatement(Connection connection) throws SQLException {if (mappedStatement.getResultSetType() ! null) {return connection.createStatement(mappedStatement.getResultSetType().getValue(), ResultSet.CONCUR_READ_ONLY);} else {return connection.createStatement();}}Overridepublic void parameterize(Statement statement) throws SQLException {// N/A}}
5. PreparedStatementHandler
PreparedStatementHandler底层依赖PreparedStatement对象来完成数据库的相关操作在调用parameterize()方法完成SQL语句的参数绑定代码也比较简单。
public class PreparedStatementHandler extends BaseStatementHandler {public PreparedStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {super(executor, mappedStatement, parameter, rowBounds, resultHandler, boundSql);}Overridepublic int update(Statement statement) throws SQLException {PreparedStatement ps (PreparedStatement) statement;ps.execute();int rows ps.getUpdateCount();Object parameterObject boundSql.getParameterObject();KeyGenerator keyGenerator mappedStatement.getKeyGenerator();keyGenerator.processAfter(executor, mappedStatement, ps, parameterObject);return rows;}Overridepublic void batch(Statement statement) throws SQLException {PreparedStatement ps (PreparedStatement) statement;ps.addBatch();}Overridepublic E ListE query(Statement statement, ResultHandler resultHandler) throws SQLException {PreparedStatement ps (PreparedStatement) statement;ps.execute();return resultSetHandler.E handleResultSets(ps);}Overridepublic E CursorE queryCursor(Statement statement) throws SQLException {PreparedStatement ps (PreparedStatement) statement;ps.execute();return resultSetHandler.E handleCursorResultSets(ps);}Overrideprotected Statement instantiateStatement(Connection connection) throws SQLException {String sql boundSql.getSql();if (mappedStatement.getKeyGenerator() instanceof Jdbc3KeyGenerator) {String[] keyColumnNames mappedStatement.getKeyColumns();if (keyColumnNames null) {return connection.prepareStatement(sql, PreparedStatement.RETURN_GENERATED_KEYS);} else {return connection.prepareStatement(sql, keyColumnNames);}} else if (mappedStatement.getResultSetType() ! null) {return connection.prepareStatement(sql, mappedStatement.getResultSetType().getValue(), ResultSet.CONCUR_READ_ONLY);} else {return connection.prepareStatement(sql);}}Overridepublic void parameterize(Statement statement) throws SQLException {parameterHandler.setParameters((PreparedStatement) statement);}}
6. CallableStatementHandler
CallableStatementHandler实际就是使用CallableStatement来执行SQL语句当然它执行的是存储过程。
public class CallableStatementHandler extends BaseStatementHandler {public CallableStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {super(executor, mappedStatement, parameter, rowBounds, resultHandler, boundSql);}Overridepublic int update(Statement statement) throws SQLException {//用来调用存储过程,它提供了对输出和输入/输出参数的支持CallableStatement cs (CallableStatement) statement;cs.execute();int rows cs.getUpdateCount();Object parameterObject boundSql.getParameterObject();KeyGenerator keyGenerator mappedStatement.getKeyGenerator();keyGenerator.processAfter(executor, mappedStatement, cs, parameterObject);resultSetHandler.handleOutputParameters(cs);return rows;}Overridepublic void batch(Statement statement) throws SQLException {CallableStatement cs (CallableStatement) statement;cs.addBatch();}Overridepublic E ListE query(Statement statement, ResultHandler resultHandler) throws SQLException {CallableStatement cs (CallableStatement) statement;cs.execute();ListE resultList resultSetHandler.EhandleResultSets(cs);resultSetHandler.handleOutputParameters(cs);return resultList;}Overridepublic E CursorE queryCursor(Statement statement) throws SQLException {CallableStatement cs (CallableStatement) statement;cs.execute();CursorE resultList resultSetHandler.EhandleCursorResultSets(cs);resultSetHandler.handleOutputParameters(cs);return resultList;}Overrideprotected Statement instantiateStatement(Connection connection) throws SQLException {String sql boundSql.getSql();if (mappedStatement.getResultSetType() ! null) {return connection.prepareCall(sql, mappedStatement.getResultSetType().getValue(), ResultSet.CONCUR_READ_ONLY);} else {return connection.prepareCall(sql);}}Overridepublic void parameterize(Statement statement) throws SQLException {//注册out参数registerOutputParameters((CallableStatement) statement);parameterHandler.setParameters((CallableStatement) statement);}private void registerOutputParameters(CallableStatement cs) throws SQLException {ListParameterMapping parameterMappings boundSql.getParameterMappings();for (int i 0, n parameterMappings.size(); i n; i) {ParameterMapping parameterMapping parameterMappings.get(i);//处理存储过程的INOUT和OUT if (parameterMapping.getMode() ParameterMode.OUT || parameterMapping.getMode() ParameterMode.INOUT) {if (null parameterMapping.getJdbcType()) {throw new ExecutorException(The JDBC Type must be specified for output parameter. Parameter: parameterMapping.getProperty());} else {if (parameterMapping.getNumericScale() ! null (parameterMapping.getJdbcType() JdbcType.NUMERIC || parameterMapping.getJdbcType() JdbcType.DECIMAL)) {cs.registerOutParameter(i 1, parameterMapping.getJdbcType().TYPE_CODE, parameterMapping.getNumericScale());} else {if (parameterMapping.getJdbcTypeName() null) {cs.registerOutParameter(i 1, parameterMapping.getJdbcType().TYPE_CODE);} else {cs.registerOutParameter(i 1, parameterMapping.getJdbcType().TYPE_CODE, parameterMapping.getJdbcTypeName());}}}}}}}
