EJB 最佳实践：数据验证出现在什么地方最合适

级别：中级

package com.ibm.library;

import java.rmi.RemoteException;
import java.util.Iterator;
import java.util.List;
import javax.ejb.CreateException;
import javax.naming.NamingException;

public class LibraryDelegate implements ILibrary {

      private ILibrary library;

      public LibraryDelegate() {
          init();
      }

      public void init() {
          // Look up and obtain our session bean
          try {
              LibraryHome libraryHome =
                  (LibraryHome)EJBHomeFactory.getInstance().lookup(
                      "java:comp/env/ejb/LibraryHome", LibraryHome.class);
              library = libraryHome.create();
          } catch (NamingException e) {
              throw new RuntimeException(e);
          } catch (CreateException e) {
              throw new RuntimeException(e);
          } catch (RemoteException e) {
              throw new RuntimeException(e);
          }
      }

      // No validation required for accessor (getter) methods

      public boolean checkout(Book book) throws ApplicationException {
        // No validation required here; the object type
        //   takes care of it

          try {
              return library.checkout(book);
          } catch (RemoteException e) {
              throw new ApplicationException(e);
          }
      }

      public boolean checkout(List books) throws ApplicationException {
        // Validate list
        for (Iterator i = books.iterator(); i.hasNext(); ) {
          Object obj = i.next();
            if !(obj instanceof Book) {
            throw new ApplicationException(
              ApplicationException.VALIDATION_ERROR,
              "Only Books are allowed in the input list");
            }
        }

          try {
              return library.checkout(books);
          } catch (RemoteException e) {
              throw new ApplicationException(e);
          }
      }

      // And so on...

        public void destroy() {
          // In this case, do nothing
      }
}