java 数据库编程
1. 读写LOB
除了数字、字符串和日期之外，许多数据库还可以存储大对象，例如图片或其它数据。在SQL中，二进制大对象称为BLOB，字符型大对象称为CLOB。
要读取LOB，需要执行SELECT语句，然后在ResultSet上调用getBlob或getClob方法，这样就可以获得Blob或Clob类型的对象。要从Blob中获取二进制数据，可以调用getBytes或getInputStream。例如，如果你有一张保存图书封面图形的表，那么就可以像下面这样获取一张图像：
PreparedStatement stat = conn.prepareStatement("SELECT Cover FROM BookCovers WHERE ISBN=?");
stat.set(1, isbn);
ResultSet result = stat.executeQuery();
if(result.next()){
Blob coverBlob = result.getBlob(1);
Image coverImage = ImageIO.read(coverBlob.getBinaryStream());
}
类似地，如果获取了Clob对象，那么就可以通过调用getSubString或getCharacterStream方法来获取其中的字符数据。
要将LOB置于数据库中，需要在Connection对象上调用createBlob或createClob，然后获取一个用于该LOB的输出流或写出器，写出数据，并将该对象存储到数据库中。例如，下面展示了如何存储一张图像：
Blob coverBlob = connection.createBlob();
int offset = 0;
OutputStream out = coverBlob.setBinaryStream(offset);
ImageIO.write(coverImage, "PNG", out);
PreparedStatement stat = conn.prepareStatement("INSERT INTO Cover VALUES(?, ?)");
stat.set(1, isbn);
stat.set(2,coverBlob);
stat.executeUpdate();
2. 可滚动和可更新的结果集
要让ResultSet可以滚动个和更新，必须在创建Statement对象的时候使用下面的方式指定对应的参数：
Statement stmt = conn.createStatement(type, concurrency);
对于PreparedStatement，使用下面的方式指定参数：
PreparedStatement pstmt = conn.prepareStatement(sql, type, concurrency);
其中，type表示ResuleSet的类型，而concurrency表示是否可以使用ResuleSet来更新数据库。
type和concurrency的取值以及含义如下：
| ResultSet类的type值 | |
| 值 | 解释 |
| ResultSet.TYPE_FORWARD_ONLY | 结果集不能滚动（默认值） |
| ResultSet.TYPE_SCROLL_INSENSITIVE | 结果集可以滚动，但ResuleSet对数据库中数据变化不敏感 |
| ResultSet.TYPE_SCROLL_SENSIT IVE | 结果集可以滚动，并且ResuleSet对数据库中发生的改变敏感 |
| ResultSet类的Concurrency值 | |
| 值 | 解释 |
| ResultSet.CONCUR_READ_ONLY | 结果集不能用于更新数据库（默认值） |
| ResultSet.CONCUR_UPDATABLE | 结果集可以用于更新数据库 |
JDBC的结果集有很多类型。这些结果集有不同的特性，以满足各种需要。这在高性能的JDBC数据操作中有着重要应用。下面是一个应用实例：
package lavasoft.common; import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement; /**
* JDBC可滚动可更新感知更新结果集测试
*
* @author leizhimin 2009-12-8 20:09:03
*/
public class TestResultSet {
public static void main(String[] args) {
testScrollResultSet();
testUpdateResultSet();
} /**
* 可更新结果集更新测试
*/
public static void testUpdateResultSet() {
Connection conn = DBToolkit.getConnection();
String sql = "SELECT * FROM book";
try {
Statement stmt = conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
ResultSet rs = stmt.executeQuery(sql); System.out.println("---------原结果集--------");
while (rs.next()) {
System.out.println("[行号：" + rs.getRow() + "]\t" + rs.getString(1) + "\t" + rs.getString(2) + "\t" + rs.getString(3));
} System.out.println("---------插入一条记录--------");
rs.first();
//将光标移动到插入行上
rs.moveToInsertRow();
//构建行数据
rs.updateString(2, "xxxx");
rs.updateString(3, "x");
//插入一行
rs.insertRow(); System.out.println("-------------更新一条记录-------------");
rs.absolute(3);
//构建行数据
rs.updateString(2, "uuuu");
rs.updateString(3, "u");
rs.updateRow(); System.out.println("---------插入更新后的结果集--------");
rs = stmt.executeQuery(sql);
while (rs.next()) {
System.out.println("[行号：" + rs.getRow() + "]\t" + rs.getString(1) + "\t" + rs.getString(2) + "\t" + rs.getString(3));
}
rs.close();
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
} finally {
DBToolkit.closeConnection(conn);
}
} /**
* 可滚动结果集滚动测试
*/
public static void testScrollResultSet() {
Connection conn = DBToolkit.getConnection();
String sql = "SELECT * FROM book";
try {
Statement stmt = conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_READ_ONLY);
ResultSet rs = stmt.executeQuery(sql);
while (rs.next()) {
System.out.println("[行号：" + rs.getRow() + "]\t" + rs.getString(1) + "\t" + rs.getString(2) + "\t" + rs.getString(3));
} System.out.println("------前滚操作-----");
//将光标移动到此 ResultSet 对象的上一行
rs.previous();
rs.previous();
System.out.println("[行号：" + rs.getRow() + "]\t" + rs.getString(1) + "\t" + rs.getString(2) + "\t" + rs.getString(3)); System.out.println("------绝对定位-----");
//将光标移动到此 ResultSet 对象的给定行编号。
rs.absolute(3);
System.out.println("[行号：" + rs.getRow() + "]\t" + rs.getString(1) + "\t" + rs.getString(2) + "\t" + rs.getString(3)); System.out.println("------移动到第一行-----");
//将光标移动到此 ResultSet 对象的第一行。
if (rs.first()) {
System.out.println("[行号：" + rs.getRow() + "]\t" + rs.getString(1) + "\t" + rs.getString(2) + "\t" + rs.getString(3));
} System.out.println("------移动到最后一行-----");
//将光标移动到此 ResultSet 对象的第一行。
if (rs.last()) {
System.out.println("[行号：" + rs.getRow() + "]\t" + rs.getString(1) + "\t" + rs.getString(2) + "\t" + rs.getString(3));
} System.out.println("------移动到第一行之前-----");
//将光标移动到此 ResultSet 对象的开头，正好位于第一行之前
rs.beforeFirst();
rs.next();
System.out.println("[行号：" + rs.getRow() + "]\t" + rs.getString(1) + "\t" + rs.getString(2) + "\t" + rs.getString(3)); System.out.println("------移动到最后一行之后-----");
//将光标移动到此 ResultSet 对象的末尾，正好位于最后一行之后。
rs.afterLast();
rs.previous();
System.out.println("[行号：" + rs.getRow() + "]\t" + rs.getString(1) + "\t" + rs.getString(2) + "\t" + rs.getString(3)); System.out.println("------相对当前行做移动-----");
rs.relative(-2);
System.out.println("[行号：" + rs.getRow() + "]\t" + rs.getString(1) + "\t" + rs.getString(2) + "\t" + rs.getString(3)); rs.close();
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
} finally {
DBToolkit.closeConnection(conn);
}
}
}
控制台输出：
[行号：1] 1 aaa a
[行号：2] 2 bbb b
[行号：3] 3 ccc c
[行号：4] 4 ddd d
[行号：5] 5 eee e
[行号：6] 6 fff f
[行号：7] 7 ggg g
[行号：8] 8 hhh h
------前滚操作-----
[行号：7] 7 ggg g
------绝对定位-----
[行号：3] 3 ccc c
------移动到第一行-----
[行号：1] 1 aaa a
------移动到最后一行-----
[行号：8] 8 hhh h
------移动到第一行之前-----
[行号：1] 1 aaa a
------移动到最后一行之后-----
[行号：8] 8 hhh h
------相对当前行做移动-----
[行号：6] 6 fff f
---------原结果集--------
[行号：1] 1 aaa a
[行号：2] 2 bbb b
[行号：3] 3 ccc c
[行号：4] 4 ddd d
[行号：5] 5 eee e
[行号：6] 6 fff f
[行号：7] 7 ggg g
[行号：8] 8 hhh h
---------插入一条记录--------
-------------更新一条记录-------------
---------插入更新后的结果集--------
[行号：1] 1 aaa a
[行号：2] 2 bbb b
[行号：3] 3 uuuu u
[行号：4] 4 ddd d
[行号：5] 5 eee e
[行号：6] 6 fff f
[行号：7] 7 ggg g
[行号：8] 8 hhh h
[行号：9] 9 xxxx x Process finished with exit code 0
可保存性：设置提交时候是否关闭结果集。
ResultSet.HOLD_CURSORS_OVER_COMMIT ：在提交后结果集还可用
ResultSet.CLOSE_CURSORS_AT_COMMIT：在提交时候关闭结果集
由于这些特性比较高级，不同数据库驱动对此实现也不一样。因此在使用JDBC高级特性的时候最好做个测试，以保证程序的可靠性。
当type设置为：ResultSet.TYPE_SCROLL_INSENSITIVE 或者 ResultSet.TYPE_SCROLL_INSENSITIVE 时，游标可以移动，但是移动的位置是[1，count]，记住并不是从0开始，否则会报错。
既然可以移动，那么把移动的几个方法解释一下：
rs = statement.executeQuery(); 游标指向第一行前面的位置，这个位置是不能获取数据，否则报错：结果集没有当前行
rs.next(); // 游标下移一个位置，如果所在位置有结果集那么返回true，否则返回false
rs.previous(); // 游标上移一个位置，如果所在位置有结果集那么返回true，否则返回false
rs.first(); // 游标指向第一行的位置
rs.last(); // 游标指向最后一行的位置
rs.beforeFirst(); // 游标指向第一行前面的位置 ， 这个位置不能获取数据
rs.afterLast(); // 游标指向最后一行后面的位置，这个位置不能获取数据
rs.absolute(index); // 游标移动至index位置，index是[1,count]的任意数字，但是不能超出，否则报错
rs.relative(index); // 游标从当前位置算移动index个位置，也就是相对移动，index可以是负数，但是计算结果同样在[1,count]内
isAfterLast(); // 判断游标是否在最后一行之后。
isBeforeFirst();// 判断游标是否在第一行之前。
ifFirst() ; //判断游标是否指向结果集的第一行。
isLast(); // 判断游标是否指向结果集的最后一行。
getRow();// 得到当前游标所指向行的行号，行号从1开始，如果结果集没有行，返回0。
3. 元数据
元数据在SQL中是用来描述数据库或其组成部分的数据。我们可以获得三类元数据：关于数据库的元数据，关于结果集的元数据，关于预备语句参数的元数据。元数据是描述基本数据信息的数据，操作元数据的语法如下：
DatabaseMetaData meta=conn.getMetaData();
ResultSet mrs=meta.getTables(null,null,null,new String[]{"TABLE"});
元数据结果集中第一列代表了表目录，第二列代表了表结构模式，第三列表名，第四列表类型，第五列关于表的注释。
下面我们编写一个简单的数据库工具，通过使用元数据来浏览数据库中的所有表，该程序还展示了如何使用带缓存的行集。
方法一：直接连接数据库，代码如下：
package view; import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.nio.file.*;
import java.sql.*;
import java.util.*; import javax.sql.*;
import javax.sql.rowset.*;
import javax.swing.*; /**
* This program uses metadata to display arbitrary tables in a database.
*
* @author DELL
*/
public class ViewDB
{
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
JFrame frame = new ViewDBFrame();
frame.setTitle("ViewDB");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
});
}
} /**
* The frame that holds the data panel and the navigation buttons.
*/
class ViewDBFrame extends JFrame
{
private JButton previousButton;
private JButton nextButton;
private JButton deleteButton;
private JButton saveButton;
private DataPanel dataPanel;
private Component scrollPane;
private JComboBox<String> tableNames;
private Properties props;
private CachedRowSet crs; public ViewDBFrame()
{
tableNames = new JComboBox<String>();
tableNames.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
showTable((String) tableNames.getSelectedItem());
}
});
add(tableNames, BorderLayout.NORTH); try
{
Class.forName("com.mysql.jdbc.Driver"); // readDatabaseProperties();
try (Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","1234"))
{
DatabaseMetaData meta = conn.getMetaData();
ResultSet mrs = meta.getTables(null, null, null, new String[] { "TABLE" });
while (mrs.next())
tableNames.addItem(mrs.getString(3));
}
}
catch (SQLException e)
{
JOptionPane.showMessageDialog(this, e);
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} JPanel buttonPanel = new JPanel();
add(buttonPanel, BorderLayout.SOUTH); previousButton = new JButton("Previous");
previousButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
showPreviousRow();
}
});
buttonPanel.add(previousButton); nextButton = new JButton("Next");
nextButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
showNextRow();
}
});
buttonPanel.add(nextButton); deleteButton = new JButton("Delete");
deleteButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
deleteRow();
}
});
buttonPanel.add(deleteButton); saveButton = new JButton("Save");
saveButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
saveChanges();
}
});
buttonPanel.add(saveButton);
pack();
} /**
* Prepares the text fields for showing a new table, and shows the first row.
* @param tableName the name of the table to display
*/
public void showTable(String tableName)
{
try
{
Class.forName("com.mysql.jdbc.Driver");
try (Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","1234"))
{
// get result set
Statement stat = conn.createStatement();
ResultSet result = stat.executeQuery("SELECT * FROM " + tableName);
// copy into cached row set
RowSetFactory factory = RowSetProvider.newFactory();
crs = factory.createCachedRowSet();
crs.setTableName(tableName);
crs.populate(result);
} if (scrollPane != null) remove(scrollPane);
dataPanel = new DataPanel(crs);
scrollPane = new JScrollPane(dataPanel);
add(scrollPane, BorderLayout.CENTER);
validate();
showNextRow();
}
catch (SQLException e)
{
JOptionPane.showMessageDialog(this, e);
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} /**
* Moves to the previous table row.
*/
public void showPreviousRow()
{
try
{
if (crs == null || crs.isFirst()) return;
crs.previous();
dataPanel.showRow(crs);
}
catch (SQLException e)
{
for (Throwable t : e)
t.printStackTrace();
}
} /**
* Moves to the next table row.
*/
public void showNextRow()
{
try
{
if (crs == null || crs.isLast()) return;
crs.next();
dataPanel.showRow(crs);
}
catch (SQLException e)
{
JOptionPane.showMessageDialog(this, e);
}
} /**
* Deletes current table row.
*/
public void deleteRow()
{
try
{
Class.forName("com.mysql.jdbc.Driver");
try (Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","1234"))
{
conn.setAutoCommit(false);
crs.deleteRow();
crs.acceptChanges(conn);
if (crs.isAfterLast())
if (!crs.last()) crs = null;
dataPanel.showRow(crs);
}
}
catch (SQLException e)
{
JOptionPane.showMessageDialog(this, e);
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} /**
* Saves all changes.
*/
public void saveChanges()
{
try
{
Class.forName("com.mysql.jdbc.Driver");
try (Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","1234"))
{
conn.setAutoCommit(false);
dataPanel.setRow(crs);
crs.acceptChanges(conn);
}
}
catch (SQLException e)
{
JOptionPane.showMessageDialog(this, e);
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} // private void readDatabaseProperties() throws IOException
// {
// props = new Properties();
// try (InputStream in = Files.newInputStream(Paths.get("database.properties")))
// {
// props.load(in);
// }
// String drivers = props.getProperty("jdbc.drivers");
// if (drivers != null) System.setProperty("jdbc.drivers", drivers);
// } /**
* Gets a connection from the properties specified in the file database.properties.
* @return the database connection
*/
// private Connection getConnection() throws SQLException
// {
// String url = props.getProperty("jdbc.url");
// String username = props.getProperty("jdbc.username");
// String password = props.getProperty("jdbc.password");
//
// return DriverManager.getConnection(url, username, password);
// }
} /**
* This panel displays the contents of a result set.
*/
class DataPanel extends JPanel
{
private java.util.List<JTextField> fields; /**
* Constructs the data panel.
* @param rs the result set whose contents this panel displays
*/
public DataPanel(RowSet rs) throws SQLException
{
fields = new ArrayList<>();
setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridwidth = 1;
gbc.gridheight = 1; ResultSetMetaData rsmd = rs.getMetaData();
for (int i = 1; i <= rsmd.getColumnCount(); i++)
{
gbc.gridy = i - 1; String columnName = rsmd.getColumnLabel(i);
gbc.gridx = 0;
gbc.anchor = GridBagConstraints.EAST;
add(new JLabel(columnName), gbc); int columnWidth = rsmd.getColumnDisplaySize(i);
JTextField tb = new JTextField(columnWidth);
if (!rsmd.getColumnClassName(i).equals("java.lang.String"))
tb.setEditable(false); fields.add(tb); gbc.gridx = 1;
gbc.anchor = GridBagConstraints.WEST;
add(tb, gbc);
}
} /**
* Shows a database row by populating all text fields with the column values.
*/
public void showRow(ResultSet rs) throws SQLException
{
for (int i = 1; i <= fields.size(); i++)
{
String field = rs == null ? "" : rs.getString(i);
JTextField tb = fields.get(i - 1);
tb.setText(field);
}
} /**
* Updates changed data into the current row of the row set.
*/
public void setRow(RowSet rs) throws SQLException
{
for (int i = 1; i <= fields.size(); i++)
{
String field = rs.getString(i);
JTextField tb = fields.get(i - 1);
if (!field.equals(tb.getText()))
rs.updateString(i, tb.getText());
}
rs.updateRow();
}
}
方法二：使用database.properties配置文件，代码如下：
package view; import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.nio.file.*;
import java.sql.*;
import java.util.*;
import javax.sql.*;
import javax.sql.rowset.*;
import javax.swing.*; /**
* This program uses metadata to display arbitrary tables in a database.
*
* @author DELL
*/
public class ViewDB
{
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
JFrame frame = new ViewDBFrame();
frame.setTitle("ViewDB");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
});
}
} /**
* The frame that holds the data panel and the navigation buttons.
*/
class ViewDBFrame extends JFrame
{
private JButton previousButton;
private JButton nextButton;
private JButton deleteButton;
private JButton saveButton;
private DataPanel dataPanel;
private Component scrollPane;
private JComboBox<String> tableNames;
private Properties props;
private CachedRowSet crs; public ViewDBFrame()
{
tableNames = new JComboBox<String>();
tableNames.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
showTable((String) tableNames.getSelectedItem());
}
});
add(tableNames, BorderLayout.NORTH); try
{
readDatabaseProperties();
try (Connection conn = getConnection())
{
DatabaseMetaData meta = conn.getMetaData();
ResultSet mrs = meta.getTables(null, null, null, new String[] { "TABLE" });
while (mrs.next())
tableNames.addItem(mrs.getString(3));
}
}
catch (SQLException e)
{
JOptionPane.showMessageDialog(this, e);
}
catch (IOException e)
{
JOptionPane.showMessageDialog(this, e);
} JPanel buttonPanel = new JPanel();
add(buttonPanel, BorderLayout.SOUTH); previousButton = new JButton("Previous");
previousButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
showPreviousRow();
}
});
buttonPanel.add(previousButton); nextButton = new JButton("Next");
nextButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
showNextRow();
}
});
buttonPanel.add(nextButton); deleteButton = new JButton("Delete");
deleteButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
deleteRow();
}
});
buttonPanel.add(deleteButton); saveButton = new JButton("Save");
saveButton.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event)
{
saveChanges();
}
});
buttonPanel.add(saveButton);
pack();
} /**
* Prepares the text fields for showing a new table, and shows the first row.
* @param tableName the name of the table to display
*/
public void showTable(String tableName)
{
try
{
try (Connection conn = getConnection())
{
// get result set
Statement stat = conn.createStatement();
ResultSet result = stat.executeQuery("SELECT * FROM " + tableName);
// copy into cached row set
RowSetFactory factory = RowSetProvider.newFactory();
crs = factory.createCachedRowSet();
crs.setTableName(tableName);
crs.populate(result);
} if (scrollPane != null) remove(scrollPane);
dataPanel = new DataPanel(crs);
scrollPane = new JScrollPane(dataPanel);
add(scrollPane, BorderLayout.CENTER);
validate();
showNextRow();
}
catch (SQLException e)
{
JOptionPane.showMessageDialog(this, e);
}
} /**
* Moves to the previous table row.
*/
public void showPreviousRow()
{
try
{
if (crs == null || crs.isFirst()) return;
crs.previous();
dataPanel.showRow(crs);
}
catch (SQLException e)
{
for (Throwable t : e)
t.printStackTrace();
}
} /**
* Moves to the next table row.
*/
public void showNextRow()
{
try
{
if (crs == null || crs.isLast()) return;
crs.next();
dataPanel.showRow(crs);
}
catch (SQLException e)
{
JOptionPane.showMessageDialog(this, e);
}
} /**
* Deletes current table row.
*/
public void deleteRow()
{
try
{
try (Connection conn = getConnection())
{
conn.setAutoCommit(false);
crs.deleteRow();
crs.acceptChanges(conn);
if (crs.isAfterLast())
if (!crs.last()) crs = null;
dataPanel.showRow(crs);
}
}
catch (SQLException e)
{
JOptionPane.showMessageDialog(this, e);
}
} /**
* Saves all changes.
*/
public void saveChanges()
{
try
{
try (Connection conn = getConnection())
{
conn.setAutoCommit(false);
dataPanel.setRow(crs);
crs.acceptChanges(conn);
}
}
catch (SQLException e)
{
JOptionPane.showMessageDialog(this, e);
}
} private void readDatabaseProperties() throws IOException
{
props = new Properties();
try (InputStream in = Files.newInputStream(Paths.get("database.properties")))
{
props.load(in);
}
String drivers = props.getProperty("jdbc.drivers");
if (drivers != null) System.setProperty("jdbc.drivers", drivers);
} /**
* Gets a connection from the properties specified in the file database.properties.
* @return the database connection
*/
private Connection getConnection() throws SQLException
{
String url = props.getProperty("jdbc.url");
String username = props.getProperty("jdbc.username");
String password = props.getProperty("jdbc.password"); return DriverManager.getConnection(url, username, password);
}
} /**
* This panel displays the contents of a result set.
*/
class DataPanel extends JPanel
{
private java.util.List<JTextField> fields; /**
* Constructs the data panel.
* @param rs the result set whose contents this panel displays
*/
public DataPanel(RowSet rs) throws SQLException
{
fields = new ArrayList<>();
setLayout(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridwidth = 1;
gbc.gridheight = 1; ResultSetMetaData rsmd = rs.getMetaData();
for (int i = 1; i <= rsmd.getColumnCount(); i++)
{
gbc.gridy = i - 1; String columnName = rsmd.getColumnLabel(i);
gbc.gridx = 0;
gbc.anchor = GridBagConstraints.EAST;
add(new JLabel(columnName), gbc); int columnWidth = rsmd.getColumnDisplaySize(i);
JTextField tb = new JTextField(columnWidth);
if (!rsmd.getColumnClassName(i).equals("java.lang.String"))
tb.setEditable(false); fields.add(tb); gbc.gridx = 1;
gbc.anchor = GridBagConstraints.WEST;
add(tb, gbc);
}
} /**
* Shows a database row by populating all text fields with the column values.
*/
public void showRow(ResultSet rs) throws SQLException
{
for (int i = 1; i <= fields.size(); i++)
{
String field = rs == null ? "" : rs.getString(i);
JTextField tb = fields.get(i - 1);
tb.setText(field);
}
} /**
* Updates changed data into the current row of the row set.
*/
public void setRow(RowSet rs) throws SQLException
{
for (int i = 1; i <= fields.size(); i++)
{
String field = rs.getString(i);
JTextField tb = fields.get(i - 1);
if (!field.equals(tb.getText()))
rs.updateString(i, tb.getText());
}
rs.updateRow();
}
}
项目目录结构如下：
其中database.properties的内容如下：
#jdbc.drivers=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/test
jdbc.username=root
jdbc.password=1234
程序运行结果如下：
