平時在開發中避免不了使用大量的if else語句,但過多層的if else對於性能有很大的開銷,相似以下代碼java
public class MainStart { public static void main(String[] args) { String msgid = "MS066"; if(message.equals("MS066")){ System.out.println("MS066"); }else if (message.equals("MS034")){ System.out.println("MS034"); }else if (message.equals("MS064")){ System.out.println("MS064"); }else{ System.out.println("no msgid!"); } } }
上邊代碼只是示例,實際狀況可能不止4層算法
策略模式是一種解耦的方法,它對算法進行封裝,使得算法的調用和算法自己分離。使用策略模式客戶端代碼不須要調整,算法之間能夠互相替換,由於不一樣的算法實現的是同一個接口。將上面的代碼優化後變爲:sql
public class MainStart { public static void main(String[] args) {
OrderDictController controller=new OrderDictController(); String msgid = "MS066"; MsgInterface msgInterface=MsgContext.getInstance(msgId);
msgInterface.manage(msg,controller); } }
實現策略模式須要如下幾個步驟:dom
1.定義接口ide
import java.sql.SQLException; import org.dom4j.DocumentException; import com.huc.controller.OrderDictController; public interface MsgInterface { public void manage(String msg, OrderDictController controller) throws DocumentException, SQLException; }
2.實現接口,重寫處理邏輯性能
package com.huc.msg.imp; import java.sql.SQLException; import org.dom4j.DocumentException; import com.huc.controller.OrderDictController; import com.huc.msg.MsgInterface; public class MS003 implements MsgInterface{ @Override public void manage(String msg, OrderDictController controller) throws DocumentException, SQLException { controller.manageMs003(msg); } }
package com.huc.msg.imp; import java.sql.SQLException; import org.dom4j.DocumentException; import com.huc.controller.OrderDictController; import com.huc.msg.MsgInterface; public class MS028 implements MsgInterface{ @Override public void manage(String msg, OrderDictController controller) throws DocumentException, SQLException { controller.manageMs028(msg); } }
寫兩個做爲例子,可根據狀況自行擴展實現類優化
3.定義策略上下文,根據msgid獲取對象實例this
package com.huc.msg; import java.util.Map; public class MsgContext { public static MsgInterface getInstance(String msgId){ MsgInterface inter=null; Map<String, String> allClazz = MsgEnum.getAllClazz(); String clazz = allClazz.get(msgId); if (msgId!=null&&msgId.trim().length()>0) { try { try { inter = (MsgInterface) Class.forName(clazz).newInstance();//調用無參構造器建立實例 } catch (InstantiationException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } } catch (ClassNotFoundException e) { e.printStackTrace(); } } return inter; } }
在這一步驟中,咱們須要一種方式能夠根據msgid來反射獲取對象的實例,這裏使用枚舉來維護兩者的對應關係。spa
package com.huc.msg; import java.util.HashMap; import java.util.Map; public enum MsgEnum { MS066("MS066", "com.huc.msg.imp.MS066"), MS034("MS034", "com.huc.msg.imp.MS034"), MS064("MS064", "com.huc.msg.imp.MS064"), MS028("MS028", "com.huc.msg.imp.MS028"), MS003("MS003", "com.huc.msg.imp.MS003"), MS062("MS062", "com.huc.msg.imp.MS062"), MS154("MS154", "com.huc.msg.imp.MS154"), MS153("MS153", "com.huc.msg.imp.MS153"), MS033("MS033", "com.huc.msg.imp.MS033"); private String msgid; private String clazz; public static Map<String, String> getAllClazz() { Map<String, String> map = new HashMap<String, String>(); for (MsgEnum msgEnum : MsgEnum.values()) { map.put(msgEnum.getMsgid(), msgEnum.getClazz()); } return map; } MsgEnum(String msgid, String clazz) { this.msgid = msgid; this.clazz = clazz; } public String getMsgid() { return msgid; } public void setMsgid(String msgid) { this.msgid = msgid; } public String getClazz() { return clazz; } public void setClazz(String clazz) { this.clazz = clazz; } }
在上面的代碼中,getAllClazz()方法用於獲取全部message和對應處理類的映射關係。至此策略模式優化就已經完成了,運行MainStart能夠看到運行結果。code