ResultHandler 参数映射核心逻辑-5
一、StatementHandler
StatementHandler
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BaseStatementHandler RoutingStatementHandler(装饰器/策略：针对创建什么类型StatementHandler，做了类型判断)
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子类
PrepareStatementHandler
SimpleStatementHandler
CallableStatementHandler
1. RoutingStatementHandler
- 此处的RoutingStatementHandler 并没有特殊的实现，只是根据StatementType字段，创建不同的StatementHandler，主要功能实现只要在于SimpleStatementHandler、PreparedStatementHandler、CallableStatementHandler 三个对象
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());
}
}
2. BaseStatementHandler
- 主要实现prepare方法
@Override
public Statement prepare(Connection connection, Integer transactionTimeout) throws SQLException {
ErrorContext.instance().sql(boundSql.getSql());
Statement statement = null;
try {
//初始化 Statement 对象
statement = instantiateStatement(connection);
//设置超时时间
setStatementTimeout(statement, transactionTimeout);
//设置FetchSize
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);
}
}
3.ParameterHandler
- 实现类：DefaultParameterHandler
- 主要针对SQL中占位符?，替换实际参数内容
@Override
public void setParameters(PreparedStatement ps) {
ErrorContext.instance().activity("setting parameters").object(mappedStatement.getParameterMap().getId());
List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();
if (parameterMappings != null) {
//遍历mapping
for (int i = 0; i < parameterMappings.size(); i++) {
ParameterMapping parameterMapping = parameterMappings.get(i);
if (parameterMapping.getMode() != ParameterMode.OUT) {
Object value;
//获取参数名
String propertyName = parameterMapping.getProperty();
//获取参数值
if (boundSql.hasAdditionalParameter(propertyName)) { // issue #448 ask first for additional params
value = boundSql.getAdditionalParameter(propertyName);
} else if (parameterObject == null) {
value = null;
} else if (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {
value = parameterObject;
} else {
MetaObject metaObject = configuration.newMetaObject(parameterObject);
value = metaObject.getValue(propertyName);
}
TypeHandler typeHandler = parameterMapping.getTypeHandler();
JdbcType jdbcType = parameterMapping.getJdbcType();
if (value == null && jdbcType == null) {
jdbcType = configuration.getJdbcTypeForNull();
}
try {
//设置参数值
typeHandler.setParameter(ps, i + 1, value, jdbcType);
} catch (TypeException | SQLException e) {
throw new TypeException("Could not set parameters for mapping: " + parameterMapping + ". Cause: " + e, e);
}
}
}
}
}
4.SimpleStatementHandler
- 继承自BaseStatementHandler，主要用于实现query / update等方法
//初始化，创建创建用于操作的Statement对象
@Override
protected Statement instantiateStatement(Connection connection) throws SQLException {
if (mappedStatement.getResultSetType() == ResultSetType.DEFAULT) {
return connection.createStatement();
} else {
return connection.createStatement(mappedStatement.getResultSetType().getValue(), ResultSet.CONCUR_READ_ONLY);
}
}
// query queryCursor batch方法均直接调用Statement实现，故不介绍
//执行insert update delete 方法
@Override
public int update(Statement statement) throws SQLException {
String sql = boundSql.getSql();
Object parameterObject = boundSql.getParameterObject();
//获取主键类型
KeyGenerator keyGenerator = mappedStatement.getKeyGenerator();
int rows;
if (keyGenerator instanceof Jdbc3KeyGenerator) {
// Jdbc3KeyGenerator 类型
// 执行SQL
statement.execute(sql, Statement.RETURN_GENERATED_KEYS);
//获取影响行数
rows = statement.getUpdateCount();
//将从数据获取的主键数据放回参数列表中
keyGenerator.processAfter(executor, mappedStatement, statement, parameterObject);
} else if (keyGenerator instanceof SelectKeyGenerator) {
statement.execute(sql);
rows = statement.getUpdateCount();
//根据<selectKey>中配置的SQL语句获取主键ID，添加到参数列表中
keyGenerator.processAfter(executor, mappedStatement, statement, parameterObject);
} else {
statement.execute(sql);
rows = statement.getUpdateCount();
}
return rows;
}
5. PrepareStatementHandler
//初始化略有不同
@Override
protected Statement instantiateStatement(Connection connection) throws SQLException {
String sql = boundSql.getSql();
//主键生成策略是Jdbc3KeyGenerator
if (mappedStatement.getKeyGenerator() instanceof Jdbc3KeyGenerator) {
String[] keyColumnNames = mappedStatement.getKeyColumns();
if (keyColumnNames == null) {
//返回数据库生成的主键
return connection.prepareStatement(sql, PreparedStatement.RETURN_GENERATED_KEYS);
} else {
//insert结束后，返回指定主键列的内容
return connection.prepareStatement(sql, keyColumnNames);
}
} else if (mappedStatement.getResultSetType() == ResultSetType.DEFAULT) {
//普通类型查询
return connection.prepareStatement(sql);
} else {
//cursor
return connection.prepareStatement(sql, mappedStatement.getResultSetType().getValue(), ResultSet.CONCUR_READ_ONLY);
}
}
6.CallableStatementHandler
- 内部使用CallableStatement，调用指定存储过程， query、update方法与上一致
