高手帮忙看看这个错误怎么解决

Question

在netbeans中运行出现错误
代码如下：
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;
import javax.swing.border.*;
import javax.xml.namespace.*;
import javax.xml.parsers.*;
import javax.xml.xpath.*;
import org.w3c.dom.*;
import org.xml.sax.*;
import java.net.*;import XRSystem.DataAccess.*;
import XRSystem.Util.*;
import XRSystem.Process.*;public class StoreXMLFrame extends javax.swing.JFrame {
    
    /** Creates new form StoreXMLFrame */
    public StoreXMLFrame() {
        initComponents();
    }
 
    private void initComponents() {
        jPanel1 = new javax.swing.JPanel();
        jScrollPane1 = new javax.swing.JScrollPane();
        jTextPane1 = new javax.swing.JTextPane();
        jPanel2 = new javax.swing.JPanel();
        jButton1 = new javax.swing.JButton();
        jButton2 = new javax.swing.JButton();
        
        new XRSystem.Util.PlafView().ChangeView();
        setDefaultCloseOperation(javax.swing.WindowConstants.DISPOSE_ON_CLOSE);
        setTitle("\u5b58\u50a8XML\u6587\u6863");
        setResizable(false);
        jTextPane1.setFont(new java.awt.Font("Times New Roman", 1, 14));
        jTextPane1.setEditable(false);
        jScrollPane1.setViewportView(jTextPane1);
        
        jButton1.setFont(new java.awt.Font("宋体", 1, 14));
        jButton1.setText("\u6253\u5f00XML");
        jButton1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButton1ActionPerformed(evt);
            }
        });
        
        jButton2.setFont(new java.awt.Font("宋体", 1, 14));
        jButton2.setText("\u5b58\u50a8XML");
        jButton2.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {                
                jButton2ActionPerformed(evt);
            }
        });
        
        org.jdesktop.layout.GroupLayout jPanel2Layout = new org.jdesktop.layout.GroupLayout(jPanel2);
        jPanel2.setLayout(jPanel2Layout);
        jPanel2Layout.setHorizontalGroup(
                jPanel2Layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                .add(org.jdesktop.layout.GroupLayout.TRAILING, jPanel2Layout.createSequentialGroup()
                .add(39, 39, 39)
                .add(jButton1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 98, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED, 88, Short.MAX_VALUE)
                .add(jButton2, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 102, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .add(54, 54, 54))
                );
        jPanel2Layout.setVerticalGroup(
                jPanel2Layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                .add(jPanel2Layout.createParallelGroup(org.jdesktop.layout.GroupLayout.BASELINE)
                .add(jButton2, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 26, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .add(jButton1, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, 26, Short.MAX_VALUE))
                );
        
        org.jdesktop.layout.GroupLayout jPanel1Layout = new org.jdesktop.layout.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
                jPanel1Layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                .add(jPanel1Layout.createSequentialGroup()
                .add(jPanel1Layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                .add(jPanel2, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .add(jScrollPane1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 381, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE))
                .addContainerGap())
                );
        jPanel1Layout.setVerticalGroup(
                jPanel1Layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                .add(org.jdesktop.layout.GroupLayout.TRAILING, jPanel1Layout.createSequentialGroup()
                .add(jScrollPane1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 291, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .add(17, 17, 17)
                .add(jPanel2, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(18, Short.MAX_VALUE))
                );
        
        org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
                layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(jPanel1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 383, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                );
        layout.setVerticalGroup(
                layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                .add(layout.createSequentialGroup()
                .addContainerGap()
                .add(jPanel1, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                );
        pack();
    }// </editor-fold>
    
    private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO 将在此处添加您的处理代码：
        URL FileURL;
        boolean flag;
        try {
            FileURL = new URL("file:\\"+FilePath);
            System.out.println(FileURL.toString());
            flag=ThisXRSystem.StoreData(FileURL);
            if(flag)
                JOptionPane.showMessageDialog(this, "文档已存入数据库");
        }catch(Exception e) {
            JOptionPane.showMessageDialog(this, e);
        }
        this.dispose();
    }
    
    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO 将在此处添加您的处理代码：
        //String ThisPath = GetFileURL();
        openFile();
    }
    

Answer 1

public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new StoreXMLFrame().setVisible(true);
            }
        });
    }
    /*
    private String GetFileURL() {
        openFile();
        return FilePath;
    }
     */
    private void openFile() {
        JFileChooser chooser = new JFileChooser();
        chooser.setCurrentDirectory(new File("."));
        
        chooser.setFileFilter(new
                javax.swing.filechooser.FileFilter() {
            public boolean accept(File f) {
                return f.isDirectory() || f.getName().toLowerCase().endsWith(".xml");
            }
            public String getDescription() { return "XML files"; }
        });
        int r = chooser.showOpenDialog(this);
        if (r != JFileChooser.APPROVE_OPTION) return;
        File f = chooser.getSelectedFile();
        FilePath = f.getAbsolutePath();
        /*
        try{
            URL FileURL = new URL("file://"+FilePath);
        }catch(Exception e) {
            JOptionPane.showMessageDialog(this, e);
        }
         */
        try {
            byte[] bytes = new byte[(int) f.length()];
            new FileInputStream(f).read(bytes);
            jTextPane1.setText(new String(bytes));
            doc = builder.parse(f);
        } catch (IOException e) {
            JOptionPane.showMessageDialog(this, e);
        } catch (SAXException e) {
            JOptionPane.showMessageDialog(this, e);
        }
    }
    private javax.swing.JButton jButton1;
    private javax.swing.JButton jButton2;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPanel jPanel2;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextPane jTextPane1;
    private Document doc;
    private DocumentBuilder builder;
    private String FilePath;
    private URL FileURL;
    private StartProcess ThisXRSystem = new StartProcess();
}

Answer 2

出现错误提示如下：
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
        at XRSystem.GUI.StoreXMLFrame.openFile(StoreXMLFrame.java:189)
        at XRSystem.GUI.StoreXMLFrame.jButton1ActionPerformed(StoreXMLFrame.java:144)
        at XRSystem.GUI.StoreXMLFrame.access$000(StoreXMLFrame.java:29)
        at XRSystem.GUI.StoreXMLFrame$1.actionPerformed(StoreXMLFrame.java:58)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995)
        at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:242)
        at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236)
        at java.awt.Component.processMouseEvent(Component.java:6038)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
        at java.awt.Component.processEvent(Component.java:5803)
        at java.awt.Container.processEvent(Container.java:2058)
        at java.awt.Component.dispatchEventImpl(Component.java:4410)
        at java.awt.Container.dispatchEventImpl(Container.java:2116)
        at java.awt.Component.dispatchEvent(Component.java:4240)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4322)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3986)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3916)
        at java.awt.Container.dispatchEventImpl(Container.java:2102)
        at java.awt.Window.dispatchEventImpl(Window.java:2429)
        at java.awt.Component.dispatchEvent(Component.java:4240)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)哪位高手能指导下要怎么修改？

Answer 3

189行是      doc = builder.parse(f);
要怎样修改呢

Answer 4

判断文件是否选中
即返回的File对象是否为空

Answer 5

private void openFile() {
        JFileChooser chooser = new JFileChooser();
        chooser.setCurrentDirectory(new File("."));
        
        chooser.setFileFilter(new
                javax.swing.filechooser.FileFilter() {
            public boolean accept(File f) {
                return f.isDirectory() || f.getName().toLowerCase().endsWith(".xml");
            }
            public String getDescription() { return "XML files"; }
        });
        int r = chooser.showOpenDialog(this);
        if (r != JFileChooser.APPROVE_OPTION) return;
        File f = chooser.getSelectedFile();
        FilePath = f.getAbsolutePath();
                try {
            byte[] bytes = new byte[(int) f.length()];
            new FileInputStream(f).read(bytes);
            jTextPane1.setText(new String(bytes));
            doc = builder.parse(f);
        } catch (IOException e) {
            JOptionPane.showMessageDialog(this, e);
        } catch (SAXException e) {
            JOptionPane.showMessageDialog(this, e);
        }
    }不知道是不是这段代码有错误，高手帮忙看看

Answer 6

就是这里
File f = chooser.getSelectedFile(); 
getSelectedFile();
此方法如果返回null
那么你就会出现空指针异常了

Answer 7

if（f==null）{
   //加上你的处理代码就可以了
}

Answer 8

if（f==null）{
   return;
}

Answer 9

 File f = chooser.getSelectedFile();
  if(f==null){return;}
 FilePath = f.getAbsolutePath();
我这样改了，还是不对啊，大哥再帮看看

Answer 10

import XRSystem.DataAccess.*;
import XRSystem.Util.*;
import XRSystem.Process.*;
你的这几个包我这里没有啊

Answer 11

不大的话发给我
[email protected]

Answer 12

错了
[email protected];
打包成rar格式
然后去掉扩展名再发给我

Answer 13

你给我的还是却几个包
不过问题看出来了
是你的builder变量没有创建对象！所以此句doc = builder.parse(f); 抛出异常在此句前加一句builder=DocumentBuilderFactory.newInstance().newDocumentBuilder();
随后捕获ParserConfigurationException就可以了