how to configure java adapter to load java-debug?

[joelpeapen]

The wiki says we can set up the java debugger independently of nvim-jdtls.

My LSP is already setup with lsp-config.
How exactly do i configure the java adapter to get the LSP to trigger the command vscode.java.startDebugSession?

Calling dap.continue() gives this error:

Adapter used with attach must have a port property
jdtls: -32601: No delegateCommandHandler for vscode.java.startDebugSession

[bayramtturgutt]

Hi @joelpeapen, pls follow below, hope works for you...

To integrate the Java debugger with your existing nvim-jdtls setup, you'll need to ensure proper configuration for both nvim-dap and the Java Debug Adapter. Here’s a structured approach to resolve the issues you’re encountering:

Ensure Dependencies Are Installed:

Verify that you have nvim-dap and nvim-dap-ui installed. These plugins are crucial for handling debugging sessions in Neovim.

Configure the Java Debug Adapter:

Set up nvim-dap with the Java Debug Adapter. You need to specify the adapter's type, host, and port. Here’s a sample configuration:

    local dap = require('dap')

dap.adapters.java = {
  type = 'server',
  host = '127.0.0.1',
  port = 5005,
}

dap.configurations.java = {
  {
    type = 'java',
    name = 'Debug (Attach)',
    request = 'attach',
    hostName = '127.0.0.1',
    port = 5005,
  },
}

This setup tells nvim-dap where to find the Java Debug Adapter and how to connect to it.

Configure nvim-jdtls:

Ensure nvim-jdtls is configured correctly to work with nvim-dap. Verify that your jdtls configuration aligns with your debugging setup:

local jdtls = require('jdtls')

jdtls.setup({
  init_options = {
    bundles = {},
  },
})

Launch Your Java Application for Debugging:

Make sure your Java application is started with debugging enabled. Use the following command:
java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005 -jar your-app.jar
Adjust the port if needed to match your nvim-dap configuration.

Trigger the Debug Session:

From Neovim, you can start the debugging session using:
require('dap').continue()

Ensure the Java application is correctly listening on the port specified in your configuration.

Troubleshoot Common Errors:

Adapter used with attach must have a port property: Double-check that your dap.adapters.java configuration includes the port property.
No delegateCommandHandler for vscode.java.startDebugSession: Confirm that the Java Debug Adapter is running and that nvim-dap is correctly configured to communicate with it.

[mfussenegger]

The server definition here won't work because nvim-dap can't connect directly to a jdwp agent.
See #451 (comment) for details.

[mfussenegger]

How exactly do i configure the java adapter to get the LSP to trigger the command vscode.java.startDebugSession?

Calling dap.continue() gives this error:

Adapter used with attach must have a port property
jdtls: -32601: No delegateCommandHandler for vscode.java.startDebugSession

The error indicates that the java-debug bundle is missing.
See https://github.com/mfussenegger/nvim-jdtls?tab=readme-ov-file#java-debug-installation for instructions on how to add it. (It doesn't require nvim-jdtls, you can set the init_options/bundles via lspconfig too)

[joelpeapen]

Turns out the problem with the bundles was i concatenated vim.fn.stdpath("data") .. "/nvim/path/to/jar" which returns "~/.local/share/nvimnvim..."

my adapter looks like this:

dap.adapters.java = function(callback)
    vim.lsp.buf.execute_command({
        command = "vscode.java.startDebugSession"
    }) -- not sure how to get the port from this command
    callback({
        type = "server";
        host = "127.0.0.1";
        port = 5005;
    })
end

which returns Couldn't connect to 127.0.0.1:5005: ECONNREFUSED

should i be using vim.lsp.rpc.request()?