Question

在以下代码中，用户在文本区域中输入查询并提交查询。我正在使用NetBeans 8.0.2和Glassfish 4.1运行。

import java.awt.BorderLayout; 
import java.awt.event.*; 
import java.sql.*; 
import javax.swing.*; 

public class AddressQuery extends JFrame
{
    // Database connection
    private static final String URL =  "jdbc:derby://localhost:1527/AddressBook";
    private static final String USERNAME = "java";
    private static final String PASSWORD = "java";  

    private boolean connectedToDatabase = false;

    private Connection  connection;
    private Statement   statement;
    private ResultSet   resultSet;

    // GUI components
    private JTextArea   queryArea;
    private JButton     submitButton;
    private JTextArea   displayArea;  

    public AddressQuery() 
    {
        super("Address Query Entry");

此代码已成功连接到数据库。

        try 
        {
        // Connect to database
        connection = DriverManager.getConnection( 
                URL, USERNAME, PASSWORD );

        // Create statement to query database
        statement = connection.createStatement();
        }
        catch (SQLException sqlException ) 
        {
            // Disconnect from Database and terminate application
            System.out.println("Failure to Connect to Database - exit App");
            System.exit(1);
        }

        // Update database connection status
        connectedToDatabase =

为用户在文本区域中输入查询正确设置了GUI

        // Set up text area for user to enter queries
        queryArea = new JTextArea( 3, 100 );
        queryArea.setWrapStyleWord( true );
        queryArea.setLineWrap( true );

        JScrollPane scrollpane = new JScrollPane( queryArea, 
        ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED, 
        ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER );

        // Set up button for submitting queries
        submitButton = new JButton( "Submit Query" );

        // Set up placement of entry text area and submit button in GUI
        Box boxNorth = Box.createHorizontalBox();
        boxNorth.add( scrollpane );
        boxNorth.add( submitButton );
        add( boxNorth, BorderLayout.NORTH);

        // Set up entry of display text area in GUI
        displayArea = new JTextArea();
        displayArea.setEditable( false );
        add( new JScrollPane( displayArea ), BorderLayout.CENTER );

事件监听器，供用户处理提交的查询

        // Event listener for submit button
        submitButton.addActionListener (
            new ActionListener ()
            {
                public void actionPerformed( ActionEvent event )
                {
                    // Perform a new query
                    try
                    {
                        setQuery( queryArea.getText() );
                    }
                    catch (SQLException sqlException )
                    {
                        displayArea.append("\nError performing query - clear entry");
                    queryArea.setText( "" );
                    }
                }
            }
        );

以下是处理输入查询并打印出更新数据库以进行调试的代码。

当我输入SELECT * FROM ADDRESSES（ADDRESSES是数据库）时，我得到：

查询= SELECT * FROM ADDRESSES

完整的地址表打印输出（意味着查询成功）：

ADDRESSID FIRSTNAME LASTNAME EMAIL PHONENUMBER
1 Mike Green demo1@deitel.com 642-5088
2 Mary Brown demo2@deitel.com 555-1234

当我输入UPDATE ADDRESSES SET PHONENUMBER =＆＃39; 555-5555＆＃39;在哪里LASTNAME =＆＃39; GREEN＆＃39;，我得到：

查询=更新地址设置PHONENUMBER =＆＃39; 555-5555＆＃39;在哪里LASTNAME =＆＃39; GREEN＆＃39; 但是发生了SQL异常，我没有得到打印出数据库内容的代码。案例似乎没有影响查询失败的成功。

    // Process query
    public void setQuery( String query ) 
            throws SQLException, IllegalStateException 
    {
        // If not connected to database - display message, throw exception
        if ( !connectedToDatabase )
        {
            displayArea.append("\nNot Connected to Database");
            throw new IllegalStateException( "Not Connected to Database");
        }
        // Execute query

        System.out.println("Query = " + query);   // debug statement
        resultSet = statement.executeQuery( query );

        //start debug code
        ResultSetMetaData metaData = resultSet.getMetaData();
        int numberOfColumns = metaData.getColumnCount();
        System.out.println("Addresses Table:\n");
        for ( int i = 1; i <= numberOfColumns; i++ )
            System.out.printf( "%-8s\t", metaData.getColumnName(i));
        System.out.println();
        while (resultSet.next())
        {
            for (int i = 1; i<= numberOfColumns; i++)
                System.out.printf("%-8s\t",resultSet.getObject(i));
            System.out.println();
        }
        // end debug code

        // Indicate successful query
        displayArea.append("\nDatabase 
    }

关闭连接和主要功能的代码如下。

在JDBC代码中只有SELECT查询工作 - UPDATE，INSERT，DELETE不

0 个答案: