问题描述
java.sql.Connection类中有个方法 PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException 这个方法中参数的第二个作用是什么，代表什么意思？ 下面是org.springframework.jdbc.core.PreparedStatementCreatorFactory中的一段代码 [code=java] public PreparedStatement createPreparedStatement(Connection con) throws SQLException { PreparedStatement ps = null; if (generatedKeysColumnNames != null || returnGeneratedKeys) { try { if (generatedKeysColumnNames != null) { ps = con.prepareStatement(this.actualSql, generatedKeysColumnNames); // TODO }else { ps = con.prepareStatement(this.actualSql, PreparedStatement.RETURN_GENERATED_KEYS); } }catch (AbstractMethodError ex) { throw new InvalidDataAccessResourceUsageException( "The JDBC driver is not compliant to JDBC 3.0 and thus " + "does not support retrieval of auto-generated keys", ex); } } else if (resultSetType == ResultSet.TYPE_FORWARD_ONLY && !updatableResults) { ps = con.prepareStatement(this.actualSql); } else { ps = con.prepareStatement(this.actualSql, resultSetType, updatableResults ? ResultSet.CONCUR_UPDATABLE : ResultSet.CONCUR_READ_ONLY); } setValues(ps); return ps; } 呵呵，这个问题困惑我许久了！问题补充kimmking 写道
解决方案
finallygo 写道ms在联合主键的时候用jdbc规范里，insert时，获取自动添加的keys用的。但是翻了下mysql 5.1.13 驱动的实现第二个参数传 什么都可以，只要length > 0就可以。/** * @see Connection#prepareStatement(String, String[]) */public java.sql.PreparedStatement prepareStatement(String sql,String[] autoGenKeyColNames) throws SQLException {java.sql.PreparedStatement pStmt = prepareStatement(sql);((com.mysql.jdbc.PreparedStatement) pStmt).setRetrieveGeneratedKeys((autoGenKeyColNames != null)&& (autoGenKeyColNames.length > 0));return pStmt;}
解决方案二：
ms在联合主键的时候用
解决方案三：
/** * Creates a default <code>PreparedStatement</code> object capable * of returning the auto-generated keys designated by the given array. * This array contains the names of the columns in the target * table that contain the auto-generated keys that should be returned. * This array is ignored if the SQL * statement is not an <code>INSERT</code> statement. * <P> * An 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 SQLExceptions. * <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>. * * @param sql an SQL statement that may contain one or more '?' IN * parameter placeholders * @param columnNames an array of column names indicating the columns * that should be returned from the inserted row or rows * @return a new <code>PreparedStatement</code> object, containing the * pre-compiled statement, that is capable of returning the * auto-generated keys designated by the given array of column * names * @exception SQLException if a database access error occurs * * @since 1.4 */ PreparedStatement prepareStatement(String sql, String columnNames[])throws SQLException;