diff --git a/README.md b/README.md
index 8c8cfbc0..503cd7d5 100644
--- a/README.md
+++ b/README.md
@@ -5,6 +5,10 @@ mybatis-generator-gui is a mybatis generator GUI tool, used to easy generate myb
 
 ![MainUI](https://cloud.githubusercontent.com/assets/3505708/16178144/35eabdcc-3673-11e6-9ff7-f701754f1550.png)
 
+### Requirements
+This tools require JRE 8.0, if you have JDK or JRE installed, you can download no jre version, otherwise
+you need download jre bundled version.
+
 ### Downloads
 
 ### Building from source
diff --git a/home.png b/home.png
deleted file mode 100644
index 57d3fce8..00000000
Binary files a/home.png and /dev/null differ
diff --git a/src/main/java/com/zzg/mybatis/generator/controller/MainUIController.java b/src/main/java/com/zzg/mybatis/generator/controller/MainUIController.java
index 940a4a19..32b7cb87 100644
--- a/src/main/java/com/zzg/mybatis/generator/controller/MainUIController.java
+++ b/src/main/java/com/zzg/mybatis/generator/controller/MainUIController.java
@@ -10,6 +10,7 @@
 import com.zzg.mybatis.generator.util.DbUtil;
 import com.zzg.mybatis.generator.util.StringUtils;
 import com.zzg.mybatis.generator.util.XMLConfigHelper;
+import com.zzg.mybatis.generator.view.AlertUtil;
 import com.zzg.mybatis.generator.view.LeftDbTreeCell;
 import com.zzg.mybatis.generator.view.UIProgressCallback;
 import javafx.collections.FXCollections;
@@ -105,6 +106,7 @@ public void initialize(URL location, ResourceBundle resources) {
                     int level = leftDBTree.getTreeItemLevel(cell.getTreeItem());
                     TreeCell<String> treeCell = (TreeCell<String>) event.getSource();
                     TreeItem<String> item = treeCell.getTreeItem();
+                    item.setExpanded(true);
                     if (level == 1) {
                         DatabaseConfig selectedConfig = (DatabaseConfig) item.getGraphic().getUserData();
                         // Accept clicks only on node cells, and not on empty spaces of the TreeView
@@ -134,12 +136,12 @@ public void initialize(URL location, ResourceBundle resources) {
                         System.out.println("index: " + leftDBTree.getSelectionModel().getSelectedIndex());
                         DatabaseConfig selectedConfig = (DatabaseConfig) item.getParent().getGraphic().getUserData();
                         String schema = treeCell.getTreeItem().getValue();
-                        item.setExpanded(true);
                         try {
                             List<String> tables = DbUtil.getTableNames(selectedConfig, schema);
                             if (tables != null && tables.size() > 0) {
+                                ObservableList<TreeItem<String>> children = cell.getTreeItem().getChildren();
+                                children.clear();
                                 for (String tableName : tables) {
-                                    ObservableList<TreeItem<String>> children = cell.getTreeItem().getChildren();
                                     TreeItem<String> treeItem = new TreeItem<>();
                                     ImageView imageView = new ImageView("icons/table.png");
                                     imageView.setFitHeight(16);
@@ -219,6 +221,10 @@ public void generateCode() throws Exception {
         tableConfig.setTableName(tableNameField.getText());
         tableConfig.setDomainObjectName(domainObjectNameField.getText());
         // JDBC config
+        if (selectedDatabaseConfig == null) {
+            AlertUtil.showInfoAlert("Please select the table from left DB tree");
+            return;
+        }
         JDBCConnectionConfiguration jdbcConfig = new JDBCConnectionConfiguration();
         jdbcConfig.setDriverClass(DbType.valueOf(selectedDatabaseConfig.getDbType()).getDriverClass());
         jdbcConfig.setConnectionURL(DbUtil.getConnectionUrlWithSchema(selectedDatabaseConfig));
diff --git a/src/main/java/com/zzg/mybatis/generator/view/AlertUtil.java b/src/main/java/com/zzg/mybatis/generator/view/AlertUtil.java
new file mode 100644
index 00000000..835dd178
--- /dev/null
+++ b/src/main/java/com/zzg/mybatis/generator/view/AlertUtil.java
@@ -0,0 +1,28 @@
+package com.zzg.mybatis.generator.view;
+
+import javafx.scene.control.Alert;
+
+/**
+ * Created by Owen on 6/21/16.
+ */
+public class AlertUtil {
+
+    public static void showInfoAlert(String message) {
+        Alert alert = new Alert(Alert.AlertType.INFORMATION);
+        alert.setContentText(message);
+        alert.show();
+    }
+
+    public static void showWarnAlert(String message) {
+        Alert alert = new Alert(Alert.AlertType.WARNING);
+        alert.setContentText(message);
+        alert.show();
+    }
+
+    public static void showErrorAlert(String message) {
+        Alert alert = new Alert(Alert.AlertType.ERROR);
+        alert.setContentText(message);
+        alert.show();
+    }
+
+}
diff --git a/src/main/java/com/zzg/mybatis/generator/view/UIProgressCallback.java b/src/main/java/com/zzg/mybatis/generator/view/UIProgressCallback.java
index 7ada2b42..2bdeb03e 100644
--- a/src/main/java/com/zzg/mybatis/generator/view/UIProgressCallback.java
+++ b/src/main/java/com/zzg/mybatis/generator/view/UIProgressCallback.java
@@ -1,5 +1,6 @@
 package com.zzg.mybatis.generator.view;
 
+import javafx.scene.control.Alert;
 import javafx.scene.control.TextArea;
 import org.mybatis.generator.api.ProgressCallback;
 
@@ -48,6 +49,9 @@ public void startTask(String taskName) {
     public void done() {
         sb.append("generation done\n");
         consoleTextArea.setText(sb.toString());
+        Alert alert = new Alert(Alert.AlertType.INFORMATION);
+        alert.setContentText("Generation Completed");
+        alert.show();
     }
 
     @Override