diff --git a/src/extension.ts b/src/extension.ts
index e68ba57..f3cbc0e 100644
--- a/src/extension.ts
+++ b/src/extension.ts
@@ -5,46 +5,60 @@ import * as path from "path";
 import * as vscode from "vscode";
 import * as commands from "./commands";
 
+const status: any = {};
+
 export function activate(context: vscode.ExtensionContext) {
     vscode.commands.registerCommand(commands.JAVA_START_DEBUGSESSION, async (config) => {
-        if (Object.keys(config).length === 0) { // No launch.json in current workspace.
-            const ans = await vscode.window.showInformationMessage(
-                "\"launch.json\" is needed to start the debugger. Do you want to create it now?", "Yes", "No");
-            if (ans === "Yes") {
-                vscode.commands.executeCommand(commands.VSCODE_ADD_DEBUGCONFIGURATION);
+
+        if (!status.debugging) {
+            status.debugging = "startDebugSession";
+
+            try {
+                if (Object.keys(config).length === 0) { // No launch.json in current workspace.
+                    const ans = await vscode.window.showInformationMessage(
+                        "\"launch.json\" is needed to start the debugger. Do you want to create it now?", "Yes", "No");
+                    if (ans === "Yes") {
+                        vscode.commands.executeCommand(commands.VSCODE_ADD_DEBUGCONFIGURATION);
+                    }
+                    return;
+                } else if (config.request === "launch") {
+                    if (!config.mainClass) {
+                        vscode.window.showErrorMessage("Please specify the mainClass in the launch.json.");
+                        return;
+                    } else if (!config.classPaths || !Array.isArray(config.classPaths) || !config.classPaths.length) {
+                        config.classPaths = await resolveClasspath(config.mainClass, config.projectName);
+                    }
+                    if (!config.classPaths || !Array.isArray(config.classPaths) || !config.classPaths.length) {
+                        vscode.window.showErrorMessage("Cannot resolve the classpaths automatically, please specify the value in the launch.json.");
+                        return;
+                    }
+                } else if (config.request === "attach") {
+                    if (!config.hostName || !config.port) {
+                        vscode.window.showErrorMessage("Please specify the host name and the port of the remote debuggee in the launch.json.");
+                        return;
+                    }
+                } else {
+                    const ans = await vscode.window.showErrorMessage(
+                        // tslint:disable-next-line:max-line-length
+                        "Request type \"" + config.request + "\" is not supported. Only \"launch\" and \"attach\" are supported.", "Open launch.json");
+                    if (ans === "Open launch.json") {
+                        await vscode.commands.executeCommand(commands.VSCODE_ADD_DEBUGCONFIGURATION);
+                    }
+                    return;
+                }
+                const debugServerPort = await startDebugSession();
+                if (debugServerPort) {
+                    config.debugServer = debugServerPort;
+                    await vscode.commands.executeCommand(commands.VSCODE_STARTDEBUG, config);
+                } else {
+                    // Information for diagnostic:
+                    console.log("Cannot find a port for debugging session");
+                }
+            } catch (ex) {
+
+            } finally {
+                delete status.debugging;
             }
-            return;
-        } else if (config.request === "launch") {
-            if (!config.mainClass) {
-                vscode.window.showErrorMessage("Please specify the mainClass in the launch.json.");
-                return;
-            } else if (!config.classPaths || !Array.isArray(config.classPaths) || !config.classPaths.length) {
-                config.classPaths = await resolveClasspath(config.mainClass, config.projectName);
-            }
-            if (!config.classPaths || !Array.isArray(config.classPaths) || !config.classPaths.length) {
-                vscode.window.showErrorMessage("Cannot resolve the classpaths automatically, please specify the value in the launch.json.");
-                return;
-            }
-        } else if (config.request === "attach") {
-            if (!config.hostName || !config.port) {
-                vscode.window.showErrorMessage("Please specify the host name and the port of the remote debuggee in the launch.json.");
-                return;
-            }
-        } else {
-            const ans = await vscode.window.showErrorMessage(
-                "Request type \"" + config.request + "\" is not supported. Only \"launch\" and \"attach\" are supported.", "Open launch.json");
-            if (ans === "Open launch.json") {
-                vscode.commands.executeCommand(commands.VSCODE_ADD_DEBUGCONFIGURATION);
-            }
-            return;
-        }
-        const debugServerPort = await startDebugSession();
-        if (debugServerPort) {
-            config.debugServer = debugServerPort;
-            vscode.commands.executeCommand(commands.VSCODE_STARTDEBUG, config);
-        } else {
-            // Information for diagnostic:
-            console.log("Cannot find a port for debugging session");
         }
     });
 }