再会!
我是使用 Java DB (Derby) 的新手。我想将它嵌入到我的应用程序中。我找到了这个网站 (http://java.sun.com/developer/technicalArticles/J2SE/Desktop/javadb/) 并按照说明进行操作。我复制了部分示例代码并进行了编辑以适合我的班级。
当我运行该类时,它返回此错误:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at java.util.Properties$LineReader.readLine(Properties.java:435)
at java.util.Properties.load0(Properties.java:354)
at java.util.Properties.load(Properties.java:342)
at recordbook.ui.RecordBookDAO.loadDBProperties(RecordBookDAO.java:40)
at recordbook.ui.RecordBookDAO.<init>(RecordBookDAO.java:28)
at recordbook.ui.RecordBook.<init>(RecordBook.java:34)
at recordbook.ui.RecordBookUI.<init>(RecordBookUI.java:23)
at recordbook.ui.RecordBookUI$3.run(RecordBookUI.java:214)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:226)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:647)
at java.awt.EventQueue.access$000(EventQueue.java:96)
at java.awt.EventQueue$1.run(EventQueue.java:608)
at java.awt.EventQueue$1.run(EventQueue.java:606)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(AccessControlContext.java:105)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:617)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:275)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:200)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:190)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:185)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:177)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:138)
BUILD SUCCESSFUL (total time: 3 seconds)
这是获取 NullPointerException 的类的一部分:
private Properties dbProperties = null;
private final String dbName;
public RecordBookDAO(String recordBookName) {
this.dbName = recordBookName;
setDBSystemDir();
dbProperties = loadDBProperties();
String driverName = dbProperties.getProperty("derby.driver");
loadDatabaseDriver(driverName);
createDatabase();
}
private Properties loadDBProperties() {
InputStream dbPropInputStream = null;
dbPropInputStream = RecordBookDAO.class.getResourceAsStream("Configuration.properties");
dbProperties = new Properties();
try
{
dbProperties.load(dbPropInputStream);
}
catch (IOException ex)
{
ex.printStackTrace();
}
return dbProperties;
}
该课程的完整代码位于:http ://dl.dropbox.com/u/34926392/RecordBookDAO.java 非常感谢您的帮助!先感谢您。