mirror of https://github.com/apache/openjpa.git
131 lines
5.2 KiB
Plaintext
131 lines
5.2 KiB
Plaintext
<%--
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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--%>
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<!-- =============================================================================================== -->
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<!-- This JSP page demonstrates usage of OpenBookService to purchase Books. -->
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<!-- =============================================================================================== -->
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<%@page import="openbook.server.OpenBookService"%>
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<%@page import="openbook.domain.Book"%>
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<%@page import="openbook.domain.ShoppingCart"%>
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<%@page import="openbook.domain.PurchaseOrder"%>
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<%@page import="openbook.domain.LineItem"%>
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<%@page import="java.util.Map"%>
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<%@page import="java.util.List"%>
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<%@page import="openbook.util.JSPUtility"%>
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<%@include file="header.jsp"%>
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<div id="help">
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<h3>Composite Relation and Derived Identity</h3>
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You have just created a
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<a href="generated-html/openbook/domain/PurchaseOrder.java.html#init" type="popup">new Purchase Order
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</a>. Each Book in
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the Shopping Cart is turned into separate line item for the order and the Purchase
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Order and all its line items are inserted as new database records. All this happened with
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this <a href="generated-html/openbook/server/OpenBookServiceImpl.java.html#placeOrder" type="popup">
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few lines of Java Code</a>
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<br>
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<ul>
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<li><b>Transitive Persistence</b>:
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The line items are persisted without any <em>explicit</em> call to persist because persist operation
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<a href="generated-html/openbook/domain/PurchaseOrder.java.html#items" type="popup"> cascades
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via the order-line item relation</a>. During persist, the JPA provider generated a new
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<a href="generated-html/openbook/domain/PurchaseOrder.java.html#id" type="popup"> identity of
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the Purchase Order</a> automatically.
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</li>
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<li><b>Compound, Derived identity</b>:
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The identity generation, in this case, is more interesting if you look at the
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<a href="generated-html/openbook/domain/LineItem.java.html#id" type="popup">
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identity used by the line items</a>. Line Item uses <em>compound, derived</em>
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identity. It is <em>compound</em> because more than one field make up the identity.
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It is <em>derived</em> because one of the identity field borrows its value
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from the owning Purchase Order's identity. Because of such dependency, the persistent
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identity of a Line Item can only be assigned only after a new
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identity value for a Purchase Order gets generated during transaction commit.
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</li>
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<li><b>Composite Relation</b>: Purchase Order - Line Item relationship is by semantics,
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a composite relation. Simply stated, life time of a Line Item is completely controlled
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by the owning Purchase Order. It is noteworthy that the Line Item constructor is
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package protected to ensure that only Purchase Order can create them.
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<br>
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The Java language provides no support for composite
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relationship -- but it is a common pattern for persistent objects. The new JPA features
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of derived identity combined with orphan delete (another new feature) and cascaded
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persistent operations provides an application to reliably express a classic Master-Details
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pattern in their application.
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</li>
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</ul>
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</div>
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<div id="content" style="display: block">
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<%
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OpenBookService service = (OpenBookService)session.getAttribute(KEY_SERVICE);
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ShoppingCart cart = (ShoppingCart)session.getAttribute(KEY_CART);
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PurchaseOrder order = null;
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if (cart.isEmpty()) {
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%>
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<jsp:forward page="<%=PAGE_SEARCH%>"/>
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<%
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} else {
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order = service.placeOrder(cart);
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}
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%>
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<h3>Thank you for ordering from OpenBooks</h3>
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<p>
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<table>
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<caption>Order : <%= order.getId() %> on <%= JSPUtility.format(order.getPlacedOn()) %>
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for <%= order.getItems().size() %> Book<%= order.getItems().size() == 0 ? "" : "s" %>
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</caption>
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<thead>
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<tr>
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<th width="10em">Title</th>
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<th width="04em">Quantity</th>
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<th width="06em">Price</th>
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</tr>
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</thead>
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<tfoot>
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<tr>
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<td><A HREF="<%= PAGE_SEARCH %>">Continue Shopping</A></td>
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</tr>
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</tfoot>
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<tbody>
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<%
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int i = 0;
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List<LineItem> items = order.getItems();
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for (LineItem item : items) {
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%>
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<TR class="<%= i++%2 == 0 ? ROW_STYLE_EVEN : ROW_STYLE_ODD %>">
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<TD> <%= item.getBook().getTitle() %> </TD>
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<TD> <%= item.getQuantity() %> </TD>
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<TD> <%= JSPUtility.format(item.getBook().getPrice() * item.getQuantity()) %> </TD>
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</TR>
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<%
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}
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%>
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<TR>
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<TD>Total</TD><TD> </TD><TD><%= JSPUtility.format(order.getTotal()) %></TD>
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</TR>
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</tbody>
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</table>
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</div>
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<%@include file="footer.jsp"%>
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