Mybatis源码之Statement处理器PreparedStatementHandler（五）

PreparedStatementHandler就是调用PreparedStatement来执行SQL语句，这样在第一次执行sql语句时会进行预编译，在接下来执行相同的SQL语句时会提高数据库性能

源码如下：

/**
* @author Clinton Begin
*/
/* 使用PrepareStatement**/
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);
}
//
public int update(Statement statement) throws SQLException {
//使用PrepareStatement
PreparedStatement ps = (PreparedStatement) statement;
ps.execute();
int rows = ps.getUpdateCount();
Object parameterObject = boundSql.getParameterObject();
KeyGenerator keyGenerator = mappedStatement.getKeyGenerator();
//keyGenerator在执行之后运行
keyGenerator.processAfter(executor, mappedStatement, ps, parameterObject);
return rows;
}
//使用PrepareStatement的批处理
public void batch(Statement statement) throws SQLException {
PreparedStatement ps = (PreparedStatement) statement;
ps.addBatch();
}
//使用PrepareStatement的execute操作
public <E> List<E> query(Statement statement, ResultHandler resultHandler) throws SQLException {
PreparedStatement ps = (PreparedStatement) statement;
ps.execute();
//操作结果在ResultHandler中处理
return resultSetHandler.<E> handleResultSets(ps);
}
//获得Statement
protected Statement instantiateStatement(Connection connection) throws SQLException {
String sql = boundSql.getSql();
//根据KeyGenerator设置值的返回key的名称
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);
}
}

public void parameterize(Statement statement) throws SQLException {
parameterHandler.setParameters((PreparedStatement) statement);
}

}