Java线程非法状态异常
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时间：2020-08-13 00:29:21 来源:igfitidea点击:
Java thread illegal state exception
提问by T-student
In a pice of code in which a class start a thread calling start method.
在一段代码中，一个类启动了一个调用 start 方法的线程。
it throw an illegalstate exception. But if i call run() it gose well.
它抛出一个非法状态异常。但是如果我调用 run() ，它运行良好。
Can you expain me why ?
你能解释一下为什么吗？
class A{
void methodA(){
T t = new T();
t.start(); // illegal state exception
t.run(); ///ok
}
}
class T extends Thread{
....
....
}
real code:
真实代码：
public class FileMultiServer
{
private static Logger _logger = Logger.getLogger("FileMultiServer");
public static void main(String[] args)
{
ServerSocket serverSocket = null;
boolean listening = true;
String host = "localhost";
int porta = 4444;
InetSocketAddress addr = null;
String archiveDir = System.getProperty("java.io.tmpdir");
Aes aes = new Aes();
Properties prop = new Properties();
//load a properties file
File propFile = new File("config.properties");
try {
System.out.println(propFile.getCanonicalPath());
prop.load(new FileInputStream("config.properties"));
} catch (Exception e1) {
// TODO Auto-generated catch block
System.out.println(e1);
}
DBConnector.dbName = prop.getProperty("database");
DBConnector.ipDb = prop.getProperty("urlDb");
DBConnector.dbPort = prop.getProperty("dbport");
DBConnector.userName = prop.getProperty("dbuser");
DBConnector.password = aes.DeCrypt(prop.getProperty("dbpassword"));
String agent_address = prop.getProperty("agent_ip");
String agent_port = prop.getProperty("agent_port");
try {
WDAgent m_agent = new WDAgent(agent_address, Integer.parseInt(agent_port));
m_agent.run();
} catch (NumberFormatException e1) {
// TODO Auto-generated catch block
System.out.println("errore nell'agent");
e1.printStackTrace();
} catch (Exception e1) {
// TODO Auto-generated catch block
StringWriter errors = new StringWriter();
e1.printStackTrace(new PrintWriter(errors));
_logger.debug(e1.getMessage());
_logger.debug(errors.toString());
System.out.println(e1.getMessage());
System.out.println(errors.toString());
}
String logCfg = System.getProperty("LOG");
if (logCfg != null) DOMConfigurator.configure(logCfg); else
DOMConfigurator.configure("log4j.xml");
try
{
if (args.length == 0) {
host = "localhost";
porta = 4444;
}
else if (args.length == 1) {
porta = Integer.parseInt(args[0]);
} else if (args.length == 2) {
host = args[0];
porta = Integer.parseInt(args[1]);
} else if (args.length == 3) {
host = args[0];
porta = Integer.parseInt(args[1]);
archiveDir = args[2];
} else {
_logger.info("usage: server <host> <port> | server [port] | server");
System.exit(88);
}
} catch (Exception e) {
_logger.error(e.getMessage());
_logger.info("enter a numer for argument or nothing....");
System.exit(88);
}
_logger.info("Allocating listen to: " + host + ":" + porta);
try
{
addr = new InetSocketAddress(host, porta);
serverSocket = new ServerSocket();
serverSocket.bind(addr);
} catch (Exception e) {
_logger.error(e.getMessage());
_logger.error("Could not listen on port: " + porta);
System.exit(-1);
}
_logger.info("Server listening on " + host + "-" + addr.getAddress().getHostAddress() + ":" + porta);
while (listening) {
try {
new FileMultiServerThread(serverSocket.accept(), archiveDir).start();
} catch (Exception e) {
// TODO Auto-generated catch block
System.out.println(e);
}
}
try {
serverSocket.close();
} catch (Exception e) {
// TODO Auto-generated catch block
System.out.println(e);
}
}
}
class extends thread:
类扩展线程：
public class WDAgent extends Thread
{
private String _PID=null;
// *************************************************************************
// private - static final
// *************************************************************************
DatagramSocket socket;
boolean m_shutdown = false;
private static final Logger m_logger = Logger.getLogger(WDAgent.class);
private String getPID() {
try {
String ppid=System.getProperty("pid");
String match= "-Dpid="+ppid;
Runtime runtime = Runtime.getRuntime();
String cmd="/bin/ps -ef ";
Process process = runtime.exec(cmd);
InputStream is = process.getInputStream();
InputStreamReader osr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(osr);
String line;
while ((line = br.readLine()) != null) {
m_logger.info("line 0: "+line);
if(line.indexOf(match)!=-1 ) {
m_logger.info("line: "+line);
String[] cols=line.split(" ");
int count=0;
String val=null;
for (int k=0; k<cols.length; k++) {
if(cols[k].length()==0) continue;
count++;
if(count==3) {
// Good. I answerd the question
String pid = val;
m_logger.debug("pid processo: " + pid);
return pid;
}
val=cols[k];
}
}
}
}
catch (Exception err)
{
m_logger.error("Error retrieving PID....", err);
err.printStackTrace();
}
return null;
}
public WDAgent(String address, int port) throws IOException
{
InetSocketAddress isa = new InetSocketAddress(address, port);
socket = new DatagramSocket(isa);
m_logger.info("Agent started on (" + address + ":" + port + ")");
m_logger.info("Waiting for WD connection.");
this.start();
}
void Finalize() throws IOException
{
m_logger.info("Closing Agent.");
socket.close();
m_logger.info("Agent Closed");
}
public void Shutdown()
{
m_shutdown = true;
}
public void run()
{
byte[] buffer = new byte[1024];
int i;
while(!m_shutdown)
{
try {
String answer = "Agent PID=123456";
for (i=0; i<1024; i++)
buffer[i] = 0;
DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
socket.receive(packet);
String received = new String(packet.getData(), 0, packet.getLength());
InetAddress client = packet.getAddress();
int client_port = packet.getPort();
m_logger.info("Received " + received + " from " + client);
if ((received.indexOf("PID") > 0) && (received.indexOf("ASK") > 0))
{
if(_PID==null) {
_PID=getPID();
}
if(_PID!=null) {
answer = "Agent PID=" + _PID;
m_logger.debug("risposta: " + answer);
DatagramPacket answ_packet = new DatagramPacket(answer.getBytes(), answer.getBytes().length, client, client_port);
socket.send(answ_packet);
} else {
m_logger.error("no PID per rispondere a watchdog .... sorry");
}
}
else
m_logger.warn("Command not recognized");
}
catch(IOException e)
{
m_logger.error(e.getMessage());
}
catch(Exception e)
{
m_logger.error(e.getMessage());
}
}
}
}
采纳答案by Kayaman
Well, if you call run(), you're just calling a method in your current thread. With start()you're attempting to start the Thread, and if it has for example already been started (or it has already stopped), you'll get an IllegalStateException.
好吧，如果你调用run()，你只是在当前线程中调用一个方法。随着start()你试图启动Thread，如果有，例如已经开始（或者它已停止），你会得到一个IllegalStateException。
回答by Subhrajyoti Majumder
ummm... you have already started the WDAgent Threadat constructor, so when you are trying to start again it thorws IllegalStateException.
嗯...你已经启动了WDAgent Threadat 构造函数，所以当你试图再次启动它 thorws IllegalStateException。
回答by aalku
You wanted to start it here:
你想从这里开始：
...
try {
WDAgent m_agent = new WDAgent(agent_address, Integer.parseInt(agent_port));
m_agent.run(); // <-- Run that you wanted to be a start
} catch (NumberFormatException e1) {
...
But it was started in the constructor:
但它是在构造函数中启动的：
public WDAgent(String address, int port) throws IOException
{
InetSocketAddress isa = new InetSocketAddress(address, port);
socket = new DatagramSocket(isa);
m_logger.info("Agent started on (" + address + ":" + port + ")");
m_logger.info("Waiting for WD connection.");
this.start(); // <<----- It was already started here!!!!
}
You are running the run method twice, once in the new thread (you start it in the constructor) and one in the main thread by calling run.
您运行 run 方法两次，一次在新线程中（您在构造函数中启动它），另一次在主线程中调用 run。
