Alright, let’s get your Java app’s traffic flowing into Fiddler. You’ve already knocked out the certificate setup and got the app running via Eclipse—great start. Here’s the critical next configuration you need:

Since you’re launching the app via Eclipse’s External Tools, you need to tell the JVM to use Fiddler as a proxy and trust the custom keystore you created. Here’s how:

• Open your External Tools configuration (Run > External Tools > External Tools Configurations)
• Locate the configuration you’re using to run the Java app
• Switch to the Arguments tab
• In the VM arguments section, paste these lines (update the paths/password to match your setup):

  -Dhttp.proxyHost=127.0.0.1
  -Dhttp.proxyPort=8888
  -Dhttps.proxyHost=127.0.0.1
  -Dhttps.proxyPort=8888
  -Djavax.net.ssl.trustStore=C:\path\to\your\FiddlerKeystore
  -Djavax.net.ssl.trustStorePassword=your_keystore_password
  

  Quick notes:
  • Replace C:\path\to\your\FiddlerKeystore with the full absolute path to the keystore file you generated with keytool
  • Use the password you set when creating the keystore (if you skipped setting one, the default is usually changeit)

Double-check Fiddler is set up to capture and decrypt HTTPS traffic:

• Open Fiddler, go to Tools > Options > HTTPS
• Ensure both Capture HTTPS CONNECTs and Decrypt HTTPS traffic are checked
• If you see a prompt about trusting the Fiddler root cert, confirm it—you already exported this cert earlier, so it’s safe

• Start Fiddler first, then launch your Java app using the updated External Tools configuration
• Check Fiddler’s session list: you should start seeing HTTP/HTTPS requests from the app pop up here

If you don’t see traffic or get SSL errors:

• Proxy mismatch: Confirm Fiddler is using port 8888 (check Tools > Options > Connections in Fiddler). If it’s using a different port, update the proxyPort values in your VM args.
• Incorrect keystore path: Make sure the trustStore path is an absolute path (relative paths can be finicky in Eclipse’s External Tools).
• SSL verification failures: For testing purposes only, you can add this VM arg to bypass hostname verification:

  -Djavax.net.ssl.hostnameVerifier=com.sun.net.ssl.internal.www.protocol.https.HttpsURLConnection$DefaultHostnameVerifier
  

  Or if you need a quicker (but less secure) fix for testing:

  -Djavax.net.ssl.trustAllHosts=true
  

  Don’t use these in production environments.

内容的提问来源于stack exchange，提问作者rippergr