EJB 倡导者: 使实体 EJB 组件满足需求

...
import javax.transaction.*;
...
public class YourServlet implements HttpServlet {
    private InitialContext initCtx = new InitialContext();
    public void doGet (
		HttpServletRequest req, HttpServletResponse
    ){
		UserTransaction userTran =
		 (UserTransaction)initCtx.lookup(
	           "java:comp/UserTransaction"
		);
        
		userTran.begin();
		//Use entity to load data
		...
		userTran.commit();
    }
    ...
}

...
import javax.transaction.*;
...
public abstract class YourParentServlet implements HttpServlet {
    private InitialContext initCtx = new InitialContext();
    public final void doGet (
		HttpServletRequest req, HttpServletResponse
    ){
		UserTransaction userTran =
		 (UserTransaction)initCtx.lookup(
	           "java:comp/UserTransaction"
		);
        
		userTran.begin();
		doGetYourParent();
		userTran.commit();
    }
    protected abstract void doGetYourParent(
		HttpServletRequest req, HttpServletResponse
    );
	    ...
}

...
import javax.transaction.*;
...
public class YourServlet implements HttpServlet {
    private InitialContext initCtx = new InitialContext();
    public void doGet (
		HttpServletRequest req, HttpServletResponse
    ){
		UserTransaction userTran =
		 (UserTransaction)initCtx.lookup(
	           "java:comp/UserTransaction"
		);
        
		userTran.begin();
		ProductLocalHome home =
		 (ProductLocalHome)initCtx.lookup(
	           "java:comp/env/ProductLocal"
		);
        
		Collection products = home.findNextNFrom(last, count);
		int size = 0;
		ProductView[] results = new ProductView[products.size];
		Iterator i = products.iterator();
		ProductView product = null;
		while (i.hasNext()) {
			ProductLocal product = (ProductLocal)i.next();
			ProductView result = new ProductView();
			// Each of these used to cause a tran and SQL
			result.setSku(product.getSku());
			result.setDesc(product.getDesc());
			result.setPrice(product.getPrice());
			result.setImage(product.getImage());
			result.setData(product.getDate());
			results[size++] = result;
		}
		// Set into the HttpServletRequest
		req.setAttribute("ProductView", results);
		// Invoke the ProductView JSP (not interesting here)
         ...
		userTran.commit();
    }
    ...
}

	 extends SessionBean {
    public ProductView[] getCatalog (
		ProductKey lastKey, int count
    ){
		ProductLocalHome home =
		 (ProductLocalHome)initCtx.lookup(
	           "java:comp/env/ProductLocal"
		);
        
		// This call used to cause a trans and SQL
		Collection products = home.findNextNFrom(last, count);
		int size = 0;
		ProductView[] results = new ProductView[products.size];
		Iterator i = products.iterator();
		ProductView product = null;
		while (i.hasNext()) {
			ProductLocal product = (ProductLocal)i.next();
			ProductView result = new ProductView();
			// Each of these used to cause a tran and SQL
			result.setSku(product.getSku());
			result.setDesc(product.getDesc());
			result.setPrice(product.getPrice());
			result.setImage(product.getImage());
			result.setData(product.getDate());
			results[size++] = result;
		}
		// Instead of setting into the HttpServletRequest
		return results;
    }
    ...
}

...
public class YourServlet implements HttpServlet {
    private InitialContext initCtx = new InitialContext();
    public void doGet (
		HttpServletRequest req, HttpServletResponse
    ){
		MySessionLocalHome home =
		 (MySessionLocalHome)initCtx.lookup(
	           "java:comp/env/MySession"
		);
        
		// Get the last key field as before
		ProductView[] home.create().getProductView(last, 10);
		//Load array into HttpServletRequest and invoke JSP
    	...
	
    }
    ...
}

public abstract ProductBean extends EntityBean {
    // Here are the properties needed for the custom method
    // NOW NO LONGER ON INTERFACE TO PREVENT INDIVIDUAL ACCESS
    public abstract ProductKey getSku() ;
    public abstract void setSku(ProductKey value);
    public abstract String getDesc() ;
    public abstract void setDesc(String value);
    public abstract BigDecimal getPrice() ;
    public abstract void setPrice(BigDecimal value);
    public abstract String getImage() ;
    public abstract void setImage(String value);
    public abstract Date getDate () ;
    public abstract void setDate(Date value);
    // Probably more properties than these above
    // Here is the custom get method&
    public ProductView getProductView (
    ){
		ProductView result = new ProductView();
		// Now cannot cause a tran and SQL
		result.setSku(getSku());
		result.setDesc(getDesc());
		result.setPrice(getPrice());
		result.setImage(getImage());
		result.setDate(getDate());
		return result;
    }
    ...
}

public interface Product extends EJBLocalObject {
    public ProductView getProductView ();
    public void setProductView(ProductView value);
}

public interface ProductHome extends EJBLocalHome {
    public Product create(ProductView value);
    public Collection findNextNFrom(ProductKey last, int count);
}

public class YourSession extends SessionBean {
    public ProductView[] getCatalog (
		ProductKey lastKey, int count
    ){
		ProductHome home =
		 (ProductHome)initCtx.lookup(
	           "java:comp/env/ProductLocal"
		);
        
		// This call used to cause a trans and SQL
		Collection products = home.findNextNFrom(last, count);
		int size = 0;
		ProductView[] results = new ProductView[products.size];
		Iterator i = products.iterator();
		ProductView product = null;
		while (i.hasNext()) {
			// Treat a next on an iterator of entities like a find
			Product product = (Product)i.next();
			// Now only one call after find, which is the ideal
			results[size++] = product.getProductView();
		}
		// Instead of setting into the HttpServletRequest
		return results;
    }
    ...
}