java - 从浏览器运行 native 代码的小程序。几乎可以工作，但抛出异常

Question

编写了一个小程序以在浏览器中打开 native 代码。当我从 IDE 作为文件运行它时它可以工作，但是当我使用 glassfish 作为本地主机从浏览器运行它来提供它时，代码会抛出异常。

package rootapplet;
import java.awt.*;
import java.io.File;

public class RootApplet extends javax.swing.JApplet{
    int number;
    private File file;

    public void init(){

    //test code
        number = 42;
    }

    public void start(){
        new Exception().printStackTrace();
        try{
            File f = new File("C:\\Windows\\System32");
            ProcessBuilder pb = new ProcessBuilder("cmd","/c","start","Notepad.exe");
            pb.directory(f);
            Process process = pb.start();
            //ProcessBuilder derp = new ProcessBuilder("C:\\Windows\\System32\\Notepad.exe","myfile.txt");
            //derp.start();
            System.out.println("Words words words");
        }
        catch(Exception e){
            System.out.println("Stuff didn't work");
        }
    }
    public void paint (Graphics screen){
        Graphics screen2D = (Graphics2D) screen;
        screen2D.drawString("The square root of "+number+" is "+Math.sqrt(number),5,50);
    }
}

我在代码中保留了另一个 ProcessBuilder 方法(不是编码意义上的方法)，因为两个 ProcessBuilder 都可以工作。但是当我从本地主机运行它时，我遇到了同样的问题。我假设这是一个 IO 异常，我只是没有将正确的文件路径传递给小程序。如果是这样的话，有谁知道我应该通过什么而不是我是什么？如果没有，可能会发生什么？

堆栈跟踪

java.lang.Exception
          at rootapplet.RootApplet.start(RootApplet.java:18)
Words Words Words
          at sun.applet.AppletPanel.run(AppletPanel.java:475)
          at java.lang.Thread.run(Thread.java:745)

Java 控制台输出

security: Certificate validation succeeded using OCSP/CRL
security: Saving certificates in Deployment session certificate store
security: Saved certificates in Deployment session certificate store
security: Checking if certificate is in Internet Explorer TrustedPublisher certificate store
network: Created version ID: 1.0+
network: Created version ID: 1.0
security: Expected Main URL: http://localhost:8080/classes/rootapplet/RootApplet.class
network: Cache entry found [url: http://localhost:8080/classes/rootapplet/RootApplet.class, version: null] prevalidated=false/0
cache: Adding MemoryCache entry: http://localhost:8080/classes/rootapplet/RootApplet.class
cache: Resource http://localhost:8080/classes/rootapplet/RootApplet.class has expired.
network: Connecting http://localhost:8080/classes/rootapplet/RootApplet.class with proxy=DIRECT
network: Connecting http://localhost:8080/ with proxy=DIRECT
network: ResponseCode for http://localhost:8080/classes/rootapplet/RootApplet.class : 304
network: Encoding for http://localhost:8080/classes/rootapplet/RootApplet.class : null
network: Disconnect connection to http://localhost:8080/classes/rootapplet/RootApplet.class
network: Cache entry not found [url: http://localhost:8080/classes/, version: null]
security: Grant socket perm for http://localhost:8080/classes/ : java.security.Permissions@452267 (
("java.net.SocketPermission" "localhost" "connect,accept,resolve")
)

network: Created version ID: 1.7.0.60
network: Created version ID: 1.7.0.65
0
basic: Embedding dialogs not enabled in Configuration
network: Created version ID: 1.7.0.60
network: Created version ID: 1.7.0.65
security: SSV validation:
    running: 1.7.0_55
    requested: 1.7.0_55
    range: null
    javaVersionParam: 1.7.0_55
    Rule Set version: null
network: Created version ID: 1.7.0.55
network: Created version ID: 1.7.0.55
security: continue with running version
network: Created version ID: 1.7.0.55
network: Created version ID: 1.7
network: Created version ID: 2.2.55
security:  --- parseCommandLine converted :
into:
[]
basic: Applet loaded.
basic: Applet resized and added to parent container
basic: PERF: AppletExecutionRunnable - applet.init() BEGIN ; jvmLaunch dt 930624 us, pluginInit dt 6880938 us, TotalTime: 7811562 us
basic: Applet initialized
basic: Starting applet
basic: completed perf rollup
Stuff didn't work again
basic: Applet made visible
basic: Applet started
basic: Told clients applet is started
network: Checking for update at: https://javadl-esd-secure.oracle.com/update/blacklist
network: Checking for update at: https://javadl-esd-secure.oracle.com/update/baseline.version
network: Checking for update at: https://javadl-esd-secure.oracle.com/update/blacklisted.certs
network: Connecting https://javadl-esd-secure.oracle.com/update/blacklist with proxy=DIRECT
network: Connecting https://javadl-esd-secure.oracle.com/update/baseline.version with proxy=DIRECT
network: Connecting https://javadl-esd-secure.oracle.com/update/blacklisted.certs with proxy=DIRECT
network: Cache entry not found [url: file:/C:/Program%20Files%20(x86)/Java/jre7/lib/ext/sunec.jar, version: null]
network: Cache entry not found [url: file:/C:/Program%20Files%20(x86)/Java/jre7/lib/ext/sunjce_provider.jar, version: null]
network: Connecting http://javadl-esd-secure.oracle.com:443/ with proxy=DIRECT
network: Connecting http://javadl-esd-secure.oracle.com:443/ with proxy=DIRECT
network: Connecting http://javadl-esd-secure.oracle.com:443/ with proxy=DIRECT
security: Loading Root CA certificates from C:\Program Files (x86)\Java\jre7\lib\security\cacerts
security: Loaded Root CA certificates from C:\Program Files (x86)\Java\jre7\lib\security\cacerts
security: Loading SSL Root CA certificates from C:\Program Files (x86)\Java\jre7\lib\security\cacerts
security: Loaded SSL Root CA certificates from C:\Program Files (x86)\Java\jre7\lib\security\cacerts
security: Loading certificates from Deployment session certificate store
security: Loaded certificates from Deployment session certificate store
security: Loading certificates from Internet Explorer ROOT certificate store
security: Loaded certificates from Internet Explorer ROOT certificate store
security: Loading certificates from Deployment session certificate store
security: Loaded certificates from Deployment session certificate store
security: Loading certificates from Deployment session certificate store
security: Loaded certificates from Deployment session certificate store
network: Updating file at: C:\Users\USER_NAME\AppData\LocalLow\Sun\Java\Deployment\security\baseline.versions from url: https://javadl-esd-secure.oracle.com/update/baseline.version
network: Updating file at: C:\Users\USER_NAME\AppData\LocalLow\Sun\Java\Deployment\security\blacklisted.certs from url: https://javadl-esd-secure.oracle.com/update/blacklisted.certs
network: Created version ID: 1.7.0.60
network: Created version ID: 1.7.0.65
network: Updating file at: C:\Users\USER_NAME\AppData\LocalLow\Sun\Java\Deployment\security\blacklist.dynamic from url: https://javadl-esd-secure.oracle.com/update/blacklist
network: Created version ID: 1.7.0.60
network: Created version ID: 1.7.0.65

Answer 1

您看到的堆栈跟踪不是由抛出的异常生成的，而是由您在 start() 第一行中构造的异常生成的:

new Exception().printStackTrace();

与该堆栈跟踪混合的输出“Words Words Words”仅可见，因为没有抛出异常并且执行了 try block 的最后一行。

在您的控制台输出中，有一行“Stuff did not work Again”，该行不是由您的源生成的。

出于调试目的，扩展 catch block 可能会有所帮助:

catch(Exception e){
    System.out.println("Stuff didn't work");
    e.printStackTrace
}

也许删除令人恼火的行“new Exception().printStackTrace();”