• Install the plugin

Using lazy.nvim

return {
  'nvim-java/nvim-java',
  dependencies = {
    'nvim-java/lua-async-await',
    'nvim-java/nvim-java-core',
    'nvim-java/nvim-java-test',
    'nvim-java/nvim-java-dap',
    'MunifTanjim/nui.nvim',
    'neovim/nvim-lspconfig',
    'mfussenegger/nvim-dap',
    {
      'williamboman/mason.nvim',
      opts = {
        registries = {
          'github:nvim-java/mason-registry',
          'github:mason-org/mason-registry',
        },
      },
    }
  },
}

• Setup nvim-java before lspconfig

require('java').setup()

• Setup jdtls like you would usually do

require('lspconfig').jdtls.setup({})

Yep! That's all :)

• JavaDapConfig - DAP is autoconfigured on start up, but in case you want to force configure it again, you can use this API
• JavaTestRunCurrentClass - Run the test class in the active buffer
• JavaTestDebugCurrentClass - Debug the test class in the active buffer
• JavaTestRunCurrentMethod - Run the test method on the cursor
• JavaTestDebugCurrentMethod - Debug the test method on the cursor
• JavaTestViewLastReport - Open the last test report in a popup window

DAP

• config_dap - DAP is autoconfigured on start up, but in case you want to force configure it again, you can use this API

require('java').dap.config_dap()

Test

• run_current_class - Run the test class in the active buffer

require('java').test.run_current_class()

• debug_current_class - Debug the test class in the active buffer

require('java').test.debug_current_class()

• run_current_method - Run the test method on the cursor

require('java').test.run_current_method()

• debug_current_method - Debug the test method on the cursor

require('java').test.debug_current_method()

• view_report - Open the last test report in a popup window

require('java').test.view_last_report()

Method 1:

Neoconf can be used to manage LSP setting including jdtls. Neoconf allows global configuration as well as project vice configurations. Here is how you can set Jdtls setting on neoconf.json

{
  "lspconfig": {
    "jdtls": {
      "java.configuration.runtimes": [
        {
          "name": "JavaSE-21",
          "path": "/opt/jdk-21",
          "default": true
        }
      ]
    },
  }
}

Method 2:

Pass the settings to Jdtls setup.

require('lspconfig').jdtls.setup({
  settings = {
    java = {
      configuration = {
        runtimes = {
          {
            name = "JavaSE-21",
            path = "/opt/jdk-21",
            default = true,
          }
        }
      }
    }
  }
})

Following is the high level idea. Jdtls is the language server nvim-java communicates with. However, we don't have all the features we need just in Jdtls. So, we are loading java-test & java-debug-adapter extensions when we launch Jdtls. Once the language server is started, we communicate with the language server to do stuff.

For instance, to run the current test,

• Request Jdtls for test classes
• Request Jdtls for class paths, module paths, java executable
• Request Jdtls to start a debug session and send the port of the session back
• Prepare TCP connections to listen to the test results
• Start nvim-dap and let user interactions to be handled by nvim-dap
• Parse the test results as they come in
• Once the execution is done, open a window show the test results

  ┌────────────┐                         ┌────────────┐
  │            │                         │            │
  │   Neovim   │                         │   VSCode   │
  │            │                         │            │
  └─────▲──────┘                         └──────▲─────┘
        │                                       │
        │                                       │
        │                                       │
        │                                       │
┌───────▼───────┐                ┌──────────────▼──────────────┐
│               │                │                             │
│   nvim-java   │                │   Extension Pack for Java   │
│               │                │                             │
└───────▲───────┘                └──────────────▲──────────────┘
        │                                       │
        │                                       │
        │                                       │
        │                                       │
        │                                       │
        │              ┌───────────┐            │
        │              │           │            │
        └──────────────►   JDTLS   ◄────────────┘
                       │           │
                       └───▲───▲───┘
                           │   │
                           │   │
                           │   │
                           │   │
                           │   │
  ┌───────────────┐        │   │         ┌────────────────────────┐
  │               │        │   │         │                        │
  │   java-test   ◄────────┘   └─────────►   java-debug-adapter   │
  │               │                      │                        │
  └───────────────┘                      └────────────────────────┘