我刚开始开发Java应用程序并使用MySQL。该应用程序之前正在运行，但基本上在我重新启动计算机后，它停止工作说“连接太多”。
我知道在关闭连接时我做错了什么，但我无法理解。如果你能指出我在哪里做错了，请。
public class ProductFrame extends javax.swing.JFrame {
/**
* Creates new form ProductFrame
*/
public ProductFrame() {
initComponents();
Show_Products_In_JTable();
}
public Connection getConnection()
{
Connection con = null;
try {
con = DriverManager.getConnection("jdbc:mysql://localhost/smart-mart","root","");
return con;
} catch (SQLException ex) {
Logger.getLogger(ProductFrame.class.getName()).log(Level.SEVERE, null, ex);
return null;
}
}
public boolean checkInputs()
{
if(
txt_name.getText() == null
|| txt_price.getText() == null
|| txt_quantity.getText() == null
|| txt_arrdate.getText() == null
|| txt_minreq.getText() == null
|| txt_maxreq.getText() == null
|| txt_staff.getText() == null
){
return false;
}
else{
try{
Float.parseFloat(txt_price.getText());
return true;
}catch(Exception ex)
{
return false;
}
}
}
//** Display Date in the ItemTable ** //
//** Step 1- Create an arraylist and fill it with date **//
public ArrayList<Product> getProductList ()
{
ArrayList<Product> productList = new ArrayList<Product>();
Connection con = getConnection();
String query = "SELECT * FROM product";
Statement st;
ResultSet rs;
try {
st = con.createStatement();
rs = st.executeQuery(query);
Product product;
Show_Products_In_JTable();
while (rs.next())
{
product = new Product (rs.getInt("id"),rs.getString("name"), Float.parseFloat(rs.getString("price")),rs.getInt("quantity"), rs.getString("arrdate"), rs.getInt("minreq"),rs.getInt("maxreq"), rs.getString("staff"));
productList.add(product);
con.close();
}
} catch (SQLException ex) {
Logger.getLogger(ProductFrame.class.getName()).log(Level.SEVERE, null, ex);
}
return productList;
}
//** Stept 2- Populate the table ** //
public void Show_Products_In_JTable()
{
ArrayList<Product> list = getProductList();
DefaultTableModel model = (DefaultTableModel) J_Table_Products.getModel();
Object[] row = new Object [8];
for(int i = 0; i<list.size();i++)
{
row[0]=list.get(i).getId();
row[1]=list.get(i).getName();
row[2]=list.get(i).getPrice();
row[3]=list.get(i).getQuantity();
row[4]=list.get(i).getArrDate();
row[5]=list.get(i).getMinReq();
row[6]=list.get(i).getMaxReq();
row[7]=list.get(i).getStaff();
model.addRow(row);
}
}
// Show Data In Inputs
public void ShowItem(int index)
{
txt_id.setText(Integer.toString(getProductList().get(index).getId()));
txt_name.setText(getProductList().get(index).getName());
txt_price.setText(Float.toString(getProductList().get(index).getPrice()));
txt_quantity.setText(Integer.toString(getProductList().get(index).getQuantity()));
txt_arrdate.setText(getProductList().get(index).getArrDate());
txt_minreq.setText(Integer.toString(getProductList().get(index).getMinReq()));
txt_maxreq.setText(Integer.toString(getProductList().get(index).getMaxReq()));
txt_staff.setText(getProductList().get(index).getStaff());
}
private void btn_insertActionPerformed(java.awt.event.ActionEvent evt) {
if (checkInputs() && txt_name !=null){
try {
Connection con = getConnection();
PreparedStatement ps;
ps = con.prepareStatement("INSERT INTO product(name, price, quantity, arrdate, minreq, maxreq, staff)"+"values(?,?,?,?,?,?,?)");
ps.setString(1, txt_name.getText());
ps.setString(2, txt_price.getText());
ps.setString(3, txt_quantity.getText());
ps.setString(4, txt_arrdate.getText());
ps.setString(5 , txt_minreq.getText());
ps.setString(6 , txt_maxreq.getText());
ps.setString(7, txt_staff.getText());
ps.executeUpdate();
Show_Products_In_JTable();
JOptionPane.showMessageDialog(null, "Data Inserted");
ps.close();
} catch (SQLException ex) {
JOptionPane.showMessageDialog(null, ex.getMessage());
}
}
else{
JOptionPane.showMessageDialog(null, "One or more field empty");
}
System.out.println("Name=>" + txt_name.getText());
System.out.println("Price=>" + txt_price.getText());
System.out.println("Quantity=>" + txt_quantity.getText());
System.out.println("Arrdate=>" + txt_arrdate.getText());
System.out.println("MinReq=>" + txt_minreq.getText());
System.out.println("MaxReq=>" + txt_maxreq.getText());
System.out.println("Staff=>" + txt_staff.getText());
}
private void btn_updateActionPerformed(java.awt.event.ActionEvent evt) {
if (checkInputs() && txt_id.getText () !=null)
{
String UpdateQuery = null;
PreparedStatement ps = null;
Connection con = getConnection ();
try {
UpdateQuery = "UPDATE product SET name=?, price=?,quantity=?, arrdate=?, minreq=?,maxreq=?, staff=? WHERE id=?";
ps = con.prepareStatement(UpdateQuery);
ps.setString(1, txt_name.getText());
ps.setString(2, txt_price.getText());
ps.setString(3, txt_quantity.getText());
ps.setString(4, txt_arrdate.getText());
ps.setString(5 , txt_minreq.getText());
ps.setString(6 , txt_maxreq.getText());
ps.setString(7, txt_staff.getText());
ps.setInt(8, Integer.parseInt(txt_id.getText()));
ps.executeUpdate();
ps.close();
} catch (SQLException ex) {
Logger.getLogger(ProductFrame.class.getName()).log(Level.SEVERE, null, ex);
}
}else{
JOptionPane.showMessageDialog(null, "One or more fields are Empty");
}
}
private void btn_deleteActionPerformed(java.awt.event.ActionEvent evt) {
if (!txt_id.getText().equals(""))
{
try {
Connection con = getConnection();
PreparedStatement ps = con.prepareStatement("DELETE FROM product WHERE id = ?");
int id = Integer.parseInt(txt_id.getText());
ps.setInt(1, id);
ps.executeUpdate();
JOptionPane.showMessageDialog(null, "Item Deleted!");
ps.close();
} catch (SQLException ex) {
Logger.getLogger(ProductFrame.class.getName()).log(Level.SEVERE, null, ex);
JOptionPane.showMessageDialog(null, "Item Not Deleted!");
ex.printStackTrace();
} finally {
}
}
else{
JOptionPane.showMessageDialog(null, " Product not found. Please enter the product ID!");
}
}
private void J_Table_ProductsMouseClicked(java.awt.event.MouseEvent evt) {
int index = J_Table_Products.getSelectedRow();
ShowItem(index);
}
/**
* @param args the command line arguments
*/
public static void main(String args[]) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(ProductFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(ProductFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(ProductFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(ProductFrame.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new ProductFrame().setVisible(true);
}
});
}
下进行。
答案 0 :(得分：0)
每次调用方法getConnection时都在创建新连接但是每次程序退出函数上下文时都不会关闭它并丢失引用，因此连接将打开，直到程序运行。这种情况引发了这个问题（连接太多）。
关闭已使用它的连接，或者仅保留对一个已打开连接的引用以重复使用它，并避免使用Open-Use-Close进程。