本文翻译自Java年鉴1.4

判断数据库是否支持事务

    try {
        DatabaseMetaData dmd = connection.getMetaData();
        if (dmd.supportsTransactions()) {
            // Transactions are supported
        } else {
            // Transactions are not supported
        }
    } catch (SQLException e) {
    }

处理SQL异常
下例说明了如何取出SQL异常信息
This example demonstrates how to retrieve the information in a SQLException.

    try {
        // Execute SQL statements...
    } catch (SQLException e) {
        while (e != null) {
            // 取出表示异常原因的可读信息 Retrieve a human-readable message identifying 
            // the reason for the exception
            String message = e.getMessage();
    
            // This vendor-independent string contains a code that identifies
            // the reason for the exception.
            // The code follows the Open Group SQL conventions.
            String sqlState = e.getSQLState();
    
            // Retrieve a vendor-specific code identifying the reason for the exception.
            int errorCode = e.getErrorCode();
    
            // If it is necessary to execute code based on this error code,
            // you should ensure that the expected driver is being
            // used before using the error code.
    
            // Get driver name
            String driverName = connection.getMetaData().getDriverName();
            if (driverName.equals("Oracle JDBC Driver") && errorCode == 123) {
                // Process error...
            }
    
            // 取得下一个异常  The exception may have been chained; process the next chained exception
            e = e.getNextException();
        }
    }

设定从数据库取出的记录数
取出的固定大小可以用于statement上,这样取出的结果集都是一样的大小;
固定大小也可用于ResultSet上,这样下次的记录数就是设定的大小.
以下是使用的例子
   try {
        // Get the fetch size of a statement
        Statement stmt = connection.createStatement ();
        int fetchSize = stmt.getFetchSize();
    
        // Set the fetch size on the statement
        stmt.setFetchSize(100);
    
        // Create a result set
        ResultSet resultSet = stmt.executeQuery("SELECT * FROM my_table");
    
        // Change the fetch size on the result set
        resultSet.setFetchSize(100);
    } catch (SQLException e) {
    }

取得结果集的列名
    try {
        // Create a result set
        Statement stmt = connection.createStatement();
        ResultSet rs = stmt.executeQuery("SELECT * FROM my_table");
    
        // Get result set meta data
        ResultSetMetaData rsmd = rs.getMetaData();
        int numColumns = rsmd.getColumnCount();
    
        // 取得列名,字段序列默认从一开始  Get the column names; column indices start from 1
        for (int i=1; i<numColumns+1; i++) {
            String columnName = rsmd.getColumnName(i);
    
            // Get the name of the column's table name
            String tableName = rsmd.getTableName(i);
        }
    } catch (SQLException e) {
    }