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Fred Bricon edited this page Mar 30, 2017 · 13 revisions

Here are a few instructions to help troubleshoot vscode-java.

Enable logging

When the Java extension fails to work as expected, reading the logs is quite often a good way to understand what the problem is. The Java extension for VS Code is composed of 2 main parts, the client (VS Code) and the server (eclipse.jdt.ls), which means important information can be logged on both components.

Turn on message tracing between VS Code and the Java Language Server

It can be useful to trace the communications between VS Code and the Java Language Server. This can be achieved by enabling tracing in VS Code settings. The java.trace.server configuration can be set to verbose to provide full message logging in the Output view (select Language support for Java in the view menu). java.trace.server can take 3 values:

  • off : no trace
  • messages : logs message types exchanged between VS Code and the java server
  • verbose : logs JSON messages exchanged between VS Code and the java server

Get the vscode-java logs

When the Java extension fails to start, the first thing to look at is the VS Code console.

  • Open the command palette (F1)
  • select Developer: Toggle Developer Tools

The chrome developer tools will open. In the console tab, you will find messages like:

stderr: Mar 30, 2017 3:54:00 PM org.eclipse.lsp4j.jsonrpc.services.GenericEndpoint notify
WARNING: Unsupported notification method: $/setTraceNotification
vscode-icons is active!
Executing /Library/Java/JavaVirtualMachines/jdk-9.jdk/Contents/Home/bin/java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=1044 --add-modules=ALL-SYSTEM 
--add-opens java.base/java.util=ALL-UNNAMED --add-opens java.base/java.lang=ALL-UNNAMED 
-Declipse.application=org.eclipse.jdt.ls.core.id1 -Dosgi.bundles.defaultStartLevel=4 
-Declipse.product=org.eclipse.jdt.ls.core.product -Dlog.protocol=true -Dlog.level=ALL 
-noverify -Xmx1G -make.it.crash -jar /Users/fbricon/Dev/projects/vscode-java/server/plugins/org.eclipse.equinox.launcher_1.4.0.v20161219-1356.jar 
-configuration /Users/fbricon/Dev/projects/vscode-java/server/config_mac 
-data /Users/fbricon/Library/Application Support/Code/User/workspaceStorage/bdea6df99b92680f795ba5759e96cfc4/redhat.java/jdt_ws
View server logs at /Users/fbricon/Library/Application Support/Code/User/workspaceStorage/bdea6df99b92680f795ba5759e96cfc4/redhat.java/jdt_ws/.metadata/plugins/.log
stderr: Unrecognized option: -make.it.crash
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

Get the Java Language Server's workspace logs

The VS Code console logs above also display the path the the server logs, that might contain other informations:

View server logs at /Users/fbricon/Library/Application Support/Code/User/workspaceStorage/bdea6df99b92680f795ba5759e96cfc4/redhat.java/jdt_ws/.metadata/plugins/.log

Clean the workspace directory

In some occasions, deleting the Java Language Server workspace directory is helpful to go back to a clean slate. Generally speaking, on the different platforms, the VS Code user workspace storage area can be found under these locations :

  • Windows : %APPDATA%\Code[ - Variant]\User\workspaceStorage\
  • MacOS : $HOME/Library/Application Support/Code[ - Variant]/User/workspaceStorage/
  • Linux : $HOME/.config/Code[ - Variant]/User/workspaceStorage/

Now, if you open the vscode-java logs, you'll see something like:

Executing /Library/Java/JavaVirtualMachines/jdk-9.jdk/Contents/Home/bin/java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=1044 --add-modules=ALL-SYSTEM 
--add-opens java.base/java.util=ALL-UNNAMED --add-opens java.base/java.lang=ALL-UNNAMED 
-Declipse.application=org.eclipse.jdt.ls.core.id1 -Dosgi.bundles.defaultStartLevel=4 -Declipse.product=org.eclipse.jdt.ls.core.product -Dlog.protocol=true -Dlog.level=ALL 
-noverify -Xmx1G -jar /Users/fbricon/Dev/projects/vscode-java/server/plugins/org.eclipse.equinox.launcher_1.4.0.v20161219-1356.jar 
-configuration /Users/fbricon/Dev/projects/vscode-java/server/config_mac 
-data /Users/fbricon/Library/Application Support/Code/User/workspaceStorage/bdea6df99b92680f795ba5759e96cfc4/redhat.java/jdt_ws

The -data option here gives you the workspace directory, that is /Users/coolusername/Library/Application Support/Code/User/workspaceStorage/bdea6df99b92680f795ba5759e96cfc4/redhat.java/jdt_ws

In case a standalone Java file is open, the workspace directory will be different than the default VS Code one, so make sure you verify the value of data

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