我有一个带有“显示”按钮的简单表单，当点击时会读取“content.txt”文件的内容，并在隐藏的标签中显示文本，并在单击按钮时显示。
该项目作为netbeans项目运行时有效。通过netbeans IDE，我将项目构建并打包到jar中。当作为jar执行时，无法看到这个基本功能。
以下是完整的代码，“content.txt”位于src文件夹中。
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.net.URISyntaxException;
import java.net.URL;
public class TestForm extends javax.swing.JFrame {
public TestForm() {
initComponents();
jLabel1.setVisible(false);
}
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jButton1 = new javax.swing.JButton();
jLabel1 = new javax.swing.JLabel();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
jButton1.setText("Display");
jButton1.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
jButton1ActionPerformed(evt);
}
});
jLabel1.setBorder(new javax.swing.border.MatteBorder(null));
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(155, 155, 155)
.addComponent(jButton1))
.addGroup(layout.createSequentialGroup()
.addGap(119, 119, 119)
.addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 125, javax.swing.GroupLayout.PREFERRED_SIZE)))
.addContainerGap(156, Short.MAX_VALUE))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addGap(37, 37, 37)
.addComponent(jButton1)
.addGap(51, 51, 51)
.addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 96, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(89, Short.MAX_VALUE))
);
pack();
}// </editor-fold>
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
try {
URL dir_url = ClassLoader.getSystemResource("content.txt");
File file = new File(dir_url.toURI());
BufferedReader reader = new BufferedReader(new FileReader(file));
String line = null;
StringBuilder stringBuilder = new StringBuilder();
String ls = System.getProperty("line.separator");
while ((line = reader.readLine()) != null) {
stringBuilder.append(line);
stringBuilder.append(ls);
}
jLabel1.setText(stringBuilder.toString());
jLabel1.setVisible(true);
}
catch(URISyntaxException ex){
ex.printStackTrace();
}
catch(FileNotFoundException ex){
ex.printStackTrace();
}
catch(IOException ex){
ex.printStackTrace();
}
}
/**
* @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(TestForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(TestForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(TestForm.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(TestForm.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 TestForm().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JButton jButton1;
private javax.swing.JLabel jLabel1;
// End of variables declaration
}
当我运行可执行jar时，它不会给我一个错误，但不会显示带有内容的标签。
当我使用命令行运行jar时，我得到以下异常。
Exception in thread "main" java.lang.UnsupportedClassVersionError: TestForm : Unsupported major.minor version 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:482)
答案 0 :(得分：1)
＆＃34; java.lang.UnsupportedClassVersionError＆＃34;是因为我的netbeans使用Java 8而我试图在运行Java 7的终端上运行它。
一旦我解决了上述问题并且能够在终端中运行jar文件，我得到了一个＆＃34; java.lang.IllegalArgumentException：URI不是分层的＆＃34;这是因为我试图访问资源＆＃34; content.txt＆＃34;这是在jar文件中。
我在代码中进行了以下更改，我在其中阅读了文本文件的内容并修复了问题。
InputStream stream = getClass().getResourceAsStream("content.txt");
BufferedReader reader = new BufferedReader(new InputStreamReader(stream));