単純なプログラムを書換えよう（WebWork2編）−observer-command-singleton

はじめに

引数のあるコンストラクタをCommandに定義をWebWork2を使って書換えてみた．異なるのはControllerとModelである．Controllerにはjspからアクセスするアクセッサを追加し，ModelからはObserverへ変化を知らせるメソッド（setChanged()/notifyObserver()）がなくなった．

ファイル/ディレクトリ構成

プログラムを動かすために，以下のファイルを用意する．

counter03-1.jsp/counter03-2.jsp: ブラウザに表示するためのjsp．counter03-1.jspは最初に表示する画面，counter03-2.jspはプログラム起動後に遷移する画面．
Command.class/DecCommand.class/IncCommamd.class/CommandDispatcher.class/Controller.class/Model.class: javaのクラス
xwork.xml: WebWork2の画面遷移等を指定するファイル

ディレクトリ構成は以下のようになる．各ファイルの内容はそれぞれ後述する．

${TOMCAT_HOME}/webapps/counter/counter03-1.jsp
                              /counter03-2.jsp
                              /WEB-INF/classes/counter03/Command.class
                                                        /DecCommand.class
                                                        /IncCommand.class
                                                        /CommandDispatcher.class
                                                        /Controller.class
                                                        /Model.class
                                              /xwork.xml
                                      /lib/commons-logging.jar
                                          /ognl-2.6.3-modified.jar
                                          /oscore-2.2.1.jar
                                          /velocity-dep-1.3.1.jar
                                          /webwork-2.0.jar
                                          /xwork-1.0.jar
                                      /web.xml

URL

アクセスするためのURLは以下の通りとなる．

http://localhost:[ポート番号]/counter/counter03-1.jsp

ポート番号が8080の場合は，

http://localhost:8080/counter/counter03-1.jsp

となる．

counter03-1.jsp/counter03-2.jsp

counter02-1.jsp/counter02-2.jspを一部修正する．

<%-- counter03-1.jsp --%>
<html>
  <head>
    <title>counter03-1</title>
  </head>
  <body>
    value:0<br/>
    <form action="Counter03.action"> <%-- xwork.xmlの記述にあわせてaction属性にはCounter03を指定 --%>
      <input type="hidden" name="value" value="0""/>
      <input type="submit" name="action" value="inc"/>
      <input type="submit" name="action" value="dec"/>
    </form>
  </body>
</html>
<%-- end --%>

<%-- counter03-2.jsp --%>
<%@ taglib prefix="ww" uri="webwork" %>
<%-- WebWorkのカスタムタグを使うのでtaglibを宣言 --%>
<html>
  <head>
    <title>counter03-2</title>
  </head>
  <body>
    value:<ww:property value="value"/><br/> <%-- Controller.getValue()メソッドを使って結果を取出す．propertyはWebWorkのカスタムタグ --%>
    <form action="Counter03.action"> <%-- xwork.xmlの記述にあわせてaction属性にはCounter03を指定 --%>
      <input type="hidden" name="value" value="<ww:property value="value"/>"/>
      <input type="submit" name="action" value="inc"/>
      <input type="submit" name="action" value="dec"/>
    </form>
  </body>
</html>
<%-- end --%>

Command.java/IncCommand.java/DecCommand.java

//Command.java
package counter03;

public interface Command{
  void execute(); 
}
//end

//IncCommand.java
package counter03;

public class IncCommand implements Command{
  private Model model;

  public IncCommand(Model model){ 
    this.model=model;
  }
  public void execute(){
    model.inc();
  }
}
//end

//DecCommand.java
package counter03;

public class DecCommand implements Command{
  private Model model;

  public DecCommand(Model model){ 
    this.model=model;
  }
  public void execute(){
    model.dec();
  }
}
//end

CommandDispatcher.java

//CommandDispatcher.java
package counter03;

import java.util.Map;
import java.util.HashMap;
import java.lang.reflect.*; 

public class CommandDispatcher{
  private static Map commands=new HashMap();
  private static CommandDispatcher commandDispatcher=new CommandDispatcher();
  private static Model model;

  static{
    commands.put("inc" ,"counter03.IncCommand");
    commands.put("dec" ,"counter03.DecCommand");
  }
  private CommandDispatcher(){
  }
  public static CommandDispatcher getInstance(Model model){ 
    commandDispatcher.model=model;
    return commandDispatcher;
  }

  public Command getCommand(String command){
    Command executeCommand=null;
    try{
      executeCommand=
        (Command)Class.forName(commands.get(command).toString())
          .getConstructor(new Class[]{this.model.getClass()})
            .newInstance(new Object[]{this.model}); 
    }
    catch(ClassNotFoundException e){
      e.printStackTrace();
    }
    catch(NoSuchMethodException e){
      e.printStackTrace();
    }
    catch(InstantiationException e){
      e.printStackTrace();
    }
    catch(IllegalAccessException e){
      e.printStackTrace();
    }
    catch(InvocationTargetException e){
      e.printStackTrace();
    }
    return executeCommand;
  }
}
//end

Controller.java

//Controller.java
package counter03;

import com.opensymphony.xwork.*;

public class Controller extends ActionSupport{
  private Model model=new Model();
  private CommandDispatcher commandDispatcher=CommandDispatcher.getInstance(model);
  private String action;

  public void setValue(String value){
    model.setValue(Integer.parseInt(value));
  }
  public String getValue(){
    return Integer.toString(model.getValue());
  }
  public void setAction(String action){
    this.action=action;
  }
  public String getAction(){
    return action;
  }
  public String execute(){
    commandDispatcher.getCommand(this.getAction()).execute();
    return SUCCESS;
  }
}
//end

Model.java

//Model.java
package counter03;

public class Model{
  private int value;
  
  public Model(){
    this(0);
  }
  public Model(int value){
    setValue(value);
  }

  public int getValue(){
    return value;
  }
  public void setValue(int value){
    this.value=value;
  }

  public int inc(){
    return inc(1);
  }
  public int inc(int value){
    setValue(getValue()+value);
    return getValue();
  }
  public int dec(){
    return dec(1);
  }
  public int dec(int value){
    setValue(getValue()-value);
    return getValue();
  }
}
//end

xwork.xml

xwork.xmlも修正する．

<!-- xwork.xml -->
<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE xwork
  PUBLIC
  "-//OpenSymphony Group//XWork 1.0//EN"
  "http://www.opensymphony.com/xwork/xwork-1.0.dtd">
<xwork>
  <include file="webwork-default.xml"/>

  <package name="default" extends="webwork-default">
    <default-interceptor-ref name="defaultStack"/>

    <!-- Counter03を追加 -->
    <action name="Counter03" class="counter03.Controller">
      <result name="success" type="dispatcher">
        <param name="location">counter03-2.jsp</param>
      </result>
    </action>
  </package>
</xwork>
<!-- end -->