Code review:

1. create action and enums and util package.
2. create IconLoadUtil.java process icon file.
3. create BrowserEngineType.java control engine type.

src/com/raindrop/action/SearchBaiDu.java

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+package com.raindrop.action;
+
+import com.intellij.ide.BrowserUtil;
+import com.intellij.openapi.actionSystem.AnAction;
+import com.intellij.openapi.actionSystem.AnActionEvent;
+import com.intellij.openapi.actionSystem.PlatformDataKeys;
+import com.intellij.openapi.editor.Editor;
+import com.intellij.openapi.editor.SelectionModel;
+import com.intellij.openapi.util.text.StringUtil;
+import com.raindrop.enums.BrowserEngineType;
+import com.raindrop.util.IconLoadUtil;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.UnsupportedEncodingException;
+import java.net.URLEncoder;
+
+/**
+ * @name: com.raindrop.action.SearchBaiDu.java
+ * @description: BaiDu search action
+ * @author: Raindrop
+ * @create Time: 2018/5/16 20:47
+ */
+public class SearchBaiDu extends AnAction {
+
+    private static final Logger logger = LoggerFactory.getLogger(SearchBaiDu.class);
+
+    public SearchBaiDu() {
+        super(null, null, IconLoadUtil.loadByPath("icon/baidu.png"));
+    }
+
+    @Override
+    public void actionPerformed(AnActionEvent e) {
+        // get editor
+        final Editor editor = e.getData(PlatformDataKeys.EDITOR);
+        // get select model
+        SelectionModel selectionModel = editor.getSelectionModel();
+        // get user selected text
+        String text = selectionModel.getSelectedText();
+        if (!StringUtil.isEmpty(text)) {
+            try {
+                text = URLEncoder.encode(text, "utf-8");
+            } catch (UnsupportedEncodingException ex) {
+                logger.error("BaiDu search url encode error: {}", ex.getMessage());
+            }
+            logger.info("BaiDu search text : {}", text);
+            BrowserUtil.browse(BrowserEngineType.BAIDU_ENGINE.getEnginePath() + text);
+        }
+    }
+
+}

src/com/raindrop/action/SearchDuckDuckGo.java

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+package com.raindrop.action;
+
+import com.intellij.ide.BrowserUtil;
+import com.intellij.openapi.actionSystem.AnAction;
+import com.intellij.openapi.actionSystem.AnActionEvent;
+import com.intellij.openapi.actionSystem.PlatformDataKeys;
+import com.intellij.openapi.editor.Editor;
+import com.intellij.openapi.editor.SelectionModel;
+import com.intellij.openapi.util.text.StringUtil;
+import com.raindrop.enums.BrowserEngineType;
+import com.raindrop.util.IconLoadUtil;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.UnsupportedEncodingException;
+import java.net.URLEncoder;
+
+/**
+ * @name: com.raindrop.action.SearchDuckDuckGo.java
+ * @description: DuckDuckGo search action
+ * @author: Raindrop
+ * @create Time: 2018/5/16 20:47
+ */
+public class SearchDuckDuckGo extends AnAction {
+
+    private static final Logger logger = LoggerFactory.getLogger(SearchDuckDuckGo.class);
+
+    public SearchDuckDuckGo() {
+        super(null, null, IconLoadUtil.loadByPath("icon/duckduckgo.png"));
+    }
+
+    @Override
+    public void actionPerformed(AnActionEvent e) {
+        // get editor
+        final Editor editor = e.getData(PlatformDataKeys.EDITOR);
+        // get select model
+        SelectionModel selectionModel = editor.getSelectionModel();
+        // get user selected text
+        String text = selectionModel.getSelectedText();
+        if (!StringUtil.isEmpty(text)) {
+            try {
+                text = URLEncoder.encode(text, "utf-8");
+            } catch (UnsupportedEncodingException ex) {
+                logger.error("DuckDuckGo search url encode error: {}", ex.getMessage());
+            }
+            logger.info("DuckDuckGo search text : {}", text);
+            BrowserUtil.browse(BrowserEngineType.DUCK_ENGINE.getEnginePath() + text);
+        }
+    }
+
+}

src/com/raindrop/action/SearchGoogle.java

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+package com.raindrop.action;
+
+import com.intellij.ide.BrowserUtil;
+import com.intellij.openapi.actionSystem.AnAction;
+import com.intellij.openapi.actionSystem.AnActionEvent;
+import com.intellij.openapi.actionSystem.PlatformDataKeys;
+import com.intellij.openapi.editor.Editor;
+import com.intellij.openapi.editor.SelectionModel;
+import com.intellij.openapi.util.text.StringUtil;
+import com.raindrop.enums.BrowserEngineType;
+import com.raindrop.util.IconLoadUtil;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.UnsupportedEncodingException;
+import java.net.URLEncoder;
+
+/**
+ * @name: com.raindrop.action.SearchGoogle.java
+ * @description: Google search action
+ * @author: Raindrop
+ * @create Time: 2018/5/16 20:47
+ */
+public class SearchGoogle extends AnAction {
+
+    private static final Logger logger = LoggerFactory.getLogger(SearchGoogle.class);
+
+    public SearchGoogle() {
+        super(null, null, IconLoadUtil.loadByPath("icon/chrome.png"));
+    }
+
+    @Override
+    public void actionPerformed(AnActionEvent e) {
+        // get editor
+        final Editor editor = e.getData(PlatformDataKeys.EDITOR);
+        // get select model
+        SelectionModel selectionModel = editor.getSelectionModel();
+        // get user selected text
+        String text = selectionModel.getSelectedText();
+        if (!StringUtil.isEmpty(text)) {
+            try {
+                text = URLEncoder.encode(text, "utf-8");
+            } catch (UnsupportedEncodingException ex) {
+                logger.error("Google search url encode error: {}", ex.getMessage());
+            }
+            logger.info("Google search text : {}", text);
+            BrowserUtil.browse(BrowserEngineType.GOOGLE_ENGINE.getEnginePath() + text);
+        }
+    }
+
+}