如何应用类反射机制简化Struts应用程序的开发

1、 先定义Action FormBean:

    package com.bhsky.webis.system;
import org.apache.struts.action.*;
import javax.servlet.http.*;
   
public class UsersActionForm extends ActionForm {
private String usr_id;
private String usr_name;
public void setUsr_id(String usr_id) {
    this.usr_id = usr_id;
}
public String getUsr_id() {
    return usr_id;
}
public String getUsr_memo() {
    return usr_memo;
}
public void setUsr_name(String usr_name) {
    this.usr_name = usr_name;
}
}




2、 编写通用的为ActionFormBean赋值的方法：

    /////////////////////////////////////////////////////////////////////////////
    //Function: 完成ResultSet对象向ArrayList对象为集合的对象的转化
    //Para:sql,指定的查询Sql
   //Para:className,Sql相对应得JavaBean/FormBean类的名字
   //Return:以类className为一条记录的结果集，完成ResultSet对象向ArrayList对象为集//合的className对象的转化
  //////////////////////////////////////////////////////////////////////////////
  public ArrayList Select(String sql,String className){
    ArrayList paraList=new ArrayList();
    try{
      if (conn == null){
        Connection();
      }
      PreparedStatement stmt = conn.prepareStatement(sql);
      ResultSet rs = stmt.executeQuery();
      String recordValue="";
      Object c1=null;
      paraList=new ArrayList();
      ResultSetMetaData rsmd = rs.getMetaData();
      int columnCount = rsmd.getColumnCount();
      while (rs.next()){
          c1=Class.forName(className).newInstance();
          for (int i=1; i<=columnCount; i++) {
            if(rs.getString(rsmd.getColumnName(i))!=null){
              recordValue=rs.getString(rsmd.getColumnName(i));
            }else{
              recordValue="";
            }
Method
m=c1.getClass().getMethod(getSetMethodName(rsmd.getColumnName(i)),
new Class[]{recordValue.getClass()});
            m.invoke (c1, new Object[]{recordValue});
          }
          paraList.add(c1);
      }
    }catch(SQLException ex){
     
}catch(ClassNotFoundException e){
}catch(NoSuchMethodException e) {
}catch(InvocationTargetException e){
}catch (IllegalAccessException e){
}catch(InstantiationException e){
} finaly{
        closeConnection();
return paraList;
}
  }




3、 在JavaBean封装的商业逻辑中调用Select 方法，然后在JSP页面上显示出来：

   //Function:取得用户列表
  //Para:
  //Return:返回用户列表
  /////////////////////////////////////////////////////////////////////////////
  public ArrayList getUsers(){
      ArrayList ret=null;
      DatabaseManage db=new DatabaseManage();
      String sql=" select usr_id,usr_name "
          +" from users " ;
      ret=db.Select(sql," com.bhsky. webis.system.UsersActionForm");
      return ret;
  }




4、 在Action的execute方法中调用getUsers()方法：

   public ActionForward execute(ActionMapping actionMapping, ActionForm actionForm,
HttpServletRequest request, HttpServletResponse httpServletResponse)
   {
    /**@todo: complete the business logic here, this is just a skeleton.*/
    UsersActionForm uaf=(UsersActionForm)actionForm;
    SystemService ubb=new SystemService();
    ArrayList userList=ubb.getUsers();
    request.setAttribute("userList",userList);
    ActionForward actionForward=actionMapping.findForward(url);
    return actionForward;
  }




5、 在JSP中显示：

   <table width="700" class="1" border="1" cellspacing="1" align="center">
<tr>
  <td class="list" >用户ID</td>
  <td class="list" >姓&#160&#160名</td>
</tr>
<logic:present name="userList" scope="request">
      <logic:iterate name="userList" id="userList"
type="com.bhsky.webis.system.UsersActionForm">
<tr>
  <td class="cell1"  height="22"><bean:write name="userList"
property="usr_id"/></td>
  <td class="cell1"  height="22"><bean:write name="userList"
property="usr_name"/></td>
    </tr>
</logic:iterate>
      </logic:present>
</table>