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2007-01-29 10:00 459 查看

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我们需要确保后退按钮和多标签或窗口不会破坏应用程序，并且能够正常工作。为此，将引入一个“交谈”，它在执行搜索时开始，在用户为定单付款时结束。让我们从一个会话 Bean 入手，它将负责处理搜索操作并在结果之间导航：

package com.jboss.dvd.seam;
import [...]

@Stateful
@Name("search")
@Conversational(ifNotBegunOutcome="main")
@Scope(ScopeType.CONVERSATION)
@Interceptors(SeamInterceptor.class)
public class SearchAction
implements Search,
Serializable
{
@In(create=true)
ShoppingCart cart;

@PersistenceContext(unitName="dvd")
EntityManager em;

private int     pageSize    = 20;
private int     currentPage = 0;
private boolean hasMore     = false;

private Category category = null;
private String   title    = null;
private String   actor    = null;

@Out(scope=CONVERSATION,required=false)
List <Product> searchResults;

@Out(scope=CONVERSATION,required=false)
Map <Product, Boolean> searchSelections;

// Getters and setters for
// category, title and actor

@Begin(join=true,
processDefinition="shopping")
public String doSearch() {
currentPage=0;
updateResults();

return "browse";
}

public String nextPage() {
if (!isLastPage()) {
currentPage++;
updateResults();
}
return null;
}

public String prevPage() {
if (!isFirstPage()) {
currentPage--;
updateResults();
}
return null;
}

public boolean isLastPage() {
return (searchResults != null) &&
!hasMore;
}
public boolean isFirstPage() {
return (searchResults != null) &&
(currentPage == 0);
}

private void updateResults() {
[...]
searchResults = [...]
searchSelections = [...]
}

private Query searchQuery(String title,
String actor, Category category) {
title = (title == null) ? "%" : "%" +
title.toLowerCase() + "%";
actor = (actor == null) ? "%" : "%" +
actor.toLowerCase() + "%";

if (category == null) {
return em.createQuery(
"from Product p where lower(p.title) like " +
":title and lower(p.actor) LIKE :actor")
.setParameter("title", title)
.setParameter("actor", actor);
}
else {
return em.createQuery(
"from Product p where lower(p.title) like " +
":title and lower(p.actor) like :actor " +
"and p.category = :category")
.setParameter("title", title)
.setParameter("actor", actor)
.setParameter("category", category);
}
}

public String addToCart() {
for (Product item: searchResults) {
Boolean selected =
searchSelections.get(item);
if ( selected!=null && selected ) {
searchSelections.put(item, false);
cart.addProduct(item, 1);
}
}
return "browse";
}

@Destroy
@Remove
public void destroy() {}
}

这个有态会话 Bean 被存储在交谈的上下文中，它将存活于交谈中，并在交谈结束时消亡。购物车是由 Seam 管理的另一会话 Bean 组件，并被注入到

SearchAction

会话 Bean，这样便不会在在建立多个搜索时丢失它。

searchResults

和

searchSelections

对象将存活于当前交谈中；它们占用的内存将在交谈结束时释放。

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标签： seam jboss actor string null bean

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