hon*_*ey1 -5 java stack-overflow multithreading
在我的应用程序中,我通过IP地址通信从另一个系统数据库访问数据.
所以为此,如果数据库系统当时处于脱机状态,则在连接期间发生异常,因此在catch块中我再次调用run()方法,当它到达联机正常的应用程序执行流程时.但在这个过程中我得到"线程中的异常"Thread-1"java.lang.StackOverflowError"这个异常如何在我的场景中解决这个异常.
这是我的代码:
MAIN CLASS :-
public static void main(String args[]) {
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new LsduJFrame().setVisible(true);
}
});
new Thread(new DisplayPlazaNameLocation()).start();// i am calling here
}
DisplayPlazaNameLocation:-
public class DisplayPlazaNameLocation implements Runnable{
static String plazaNameLocation;
static Connection con;
int i =0;
public void getPlazaNameLocation(){
try {
System.out.println("in getPlazaNameLocation()==============================================");
PreparedStatement pst=con.prepareStatement("SELECT DISTINCT Plaza_Loc FROM lsdu_live");
ResultSet rs = pst.executeQuery();
while(rs.next()){
plazaNameLocation = rs.getString("Plaza_Loc");
//System.out.println(plazaNameLocation);
}
String ar[] = plazaNameLocation.split(",");
jLabel199.setText("<html>"+ar[0]+"<br>"+ar[1]+"</html>");
rs.close();
pst.close();
con.close();
} catch (SQLException ex) {
run();
}
}
@Override
public void run(){
try {
Class.forName(DB_DRIVER_CLASS);
con= DriverManager.getConnection(DB_URL[0],DB_USERNAME,DB_PASSWORD);
if(con != null){
this.getPlazaNameLocation();}
} catch (ClassNotFoundException ex) {
run();
} catch (SQLException ex) {
run();
}
}
}
执行一段时间后,我得到了这个例外 Exception in thread "Thread-1" java.lang.StackOverflowError
假设我在获得此异常之前解决了Connection问题,应用程序正常工作,但在获得此异常后,在此时获取此异常后不再使用resolve我需要关闭应用程序并在此时再次打开它正在运行. How to resolve this issue with respect to my code ?
stackTrace() data:-
Exception in thread "Thread-1" java.lang.StackOverflowError
at java.lang.Exception.<init>(Exception.java:66)
at java.sql.SQLException.<init>(SQLException.java:70)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1073)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:987)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:982)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:927)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:435)
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:381)
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:305)
at java.sql.DriverManager.getConnection(DriverManager.java:571)
at java.sql.DriverManager.getConnection(DriverManager.java:215)
at lsdu_application.DisplayPlazaNameLocation.run(DisplayPlazaNameLocation.java:47)
at lsdu_application.DisplayPlazaNameLocation.run(DisplayPlazaNameLocation.java:59)
at
在你的run方法中,你打电话getPlazaNameLocation.如果SQL失败,则run再次调用.这会导致这两种方法之间出现无限的"循环"(递归),每次调用都会添加到调用堆栈中,最终会导致调用StackOverflowError.
run在SQLException的情况下调用？您应该处理catch块中的错误,而不是重新启动您的功能.删除该电话并获取有关您SQLException使用的信息e.printStackTrace().run手动打电话.应该使用调用Thread.start().编辑:如果你真的想重新尝试数据库操作,以防它失败,试试这个:
public void getPlazaNameLocation() throws SQLException {
//same code, but remove the try/catch blocks and
// especially the run()!
}
@Override
public void run(){
try {
Class.forName(DB_DRIVER_CLASS);
con = DriverManager.getConnection(DB_URL[0],DB_USERNAME,DB_PASSWORD);
} catch (ClassNotFoundException ex) {
e.printStackTrace();
//fail here since no driver was found
return;
}
boolean retry = true;
while(retry){
try {
getPlazaNameLocation();
retry = false;
} catch (SQLException ex) {
//if we arrive here, "retry" will still have a value of true
}
}
}
请注意,我不建议通过与数据库断开连接的垃圾邮件请求,就像这段代码一样.
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