struts2实现CRUD(增删改查)

小鱼儿 2022-08-26 14:09 292阅读 0赞

CRUD是Create（创建）、Read（读取）、Update（更新）和Delete（删除）的缩写，它是普通应用程序的缩影。如果您掌握了某框架的CRUD编写，那么意味可以使用该框架创建普通应用程序了，所以大家使用新框架开发OLTP（Online Transaction Processing）应用程序时，首先会研究一下如何编写CRUD。这类似于大家在学习新编程语言时喜欢编写“Hello World”。

本文旨在讲述Struts 2上的CRUD开发，所以为了例子的简单易懂，我不会花时间在数据库的操作上。取而代之的是一个模拟数据库的哈希表（Hash Map）。

## 具体实现 ##

首先，让我们看看的“冒牌”的DAO（Data Access Object，数据访问对象），代码如下：

![None.gif][] package  tutorial.dao;  
![None.gif][]  
![None.gif][] import  java.util.Collection;  
![None.gif][] import  java.util.concurrent.ConcurrentHashMap;  
![None.gif][] import  java.util.concurrent.ConcurrentMap;  
![None.gif][]  
![None.gif][] import  tutorial.model.Book;  
![None.gif][]  
![ExpandedBlockStart.gif][] public  class  BookDao  \{  
![InBlock.gif][]privatestaticfinal BookDao instance;  
![InBlock.gif][]privatestaticfinal ConcurrentMap<String, Book> data;  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]static\{  
![InBlock.gif][] instance =new BookDao();  
![InBlock.gif][] data =new ConcurrentHashMap<String, Book>();  
![InBlock.gif][] data.put("978-0735619678", new Book("978-0735619678", "Code Complete, Second Edition", 32.99));  
![InBlock.gif][] data.put("978-0596007867", new Book("978-0596007867", "The Art of Project Management", 35.96));  
![InBlock.gif][] data.put("978-0201633610", new Book("978-0201633610", "Design Patterns: Elements of Reusable Object-Oriented Software", 43.19));  
![InBlock.gif][] data.put("978-0596527341", new Book("978-0596527341", "Information Architecture for the World Wide Web: Designing Large-Scale Web Sites", 25.19));  
![InBlock.gif][] data.put("978-0735605350", new Book("978-0735605350", "Software Estimation: Demystifying the Black Art", 25.19));  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]private BookDao() \{\}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]publicstatic BookDao getInstance() \{  
![InBlock.gif][]return instance;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]public Collection<Book> getBooks() \{  
![InBlock.gif][]return data.values();  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]public Book getBook(String isbn) \{  
![InBlock.gif][]return data.get(isbn);  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]publicvoid storeBook(Book book) \{  
![InBlock.gif][] data.put(book.getIsbn(), book);  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]publicvoid removeBook(String isbn) \{  
![InBlock.gif][] data.remove(isbn);  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]publicvoid removeBooks(String\[\] isbns) \{  
![ExpandedSubBlockStart.gif][]for(String isbn : isbns) \{  
![InBlock.gif][] data.remove(isbn);  
![ExpandedSubBlockEnd.gif][] \}  
![ExpandedSubBlockEnd.gif][] \}  
![ExpandedBlockEnd.gif][]\}

*清单1 src/tutorial/dao/BookDao.java*

以上代码相信不用解释大家也清楚，我使用ConcurrentMap数据结构存储Book对象，这主要是为了方便检索和保存Book对象；另外，我还将data变量设为静态唯一来模拟应用程序的数据库。

接下来是的数据模型Book类，代码如下：

![None.gif][] package  tutorial.model;  
![None.gif][]  
![ExpandedBlockStart.gif][] public  class  Book  \{  
![InBlock.gif][]private String isbn;  
![InBlock.gif][]private String title;  
![InBlock.gif][]privatedouble price;  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]public Book() \{  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]public Book(String isbn, String title, double price) \{  
![InBlock.gif][]this.isbn = isbn;  
![InBlock.gif][]this.title = title;  
![InBlock.gif][]this.price = price;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]public String getIsbn() \{  
![InBlock.gif][]return isbn;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]publicvoid setIsbn(String isbn) \{  
![InBlock.gif][]this.isbn = isbn;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]publicdouble getPrice() \{  
![InBlock.gif][]return price;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]publicvoid setPrice(double price) \{  
![InBlock.gif][]this.price = price;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]public String getTitle() \{  
![InBlock.gif][]return title;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]publicvoid setTitle(String title) \{  
![InBlock.gif][]this.title = title;  
![ExpandedSubBlockEnd.gif][] \}  
![ExpandedBlockEnd.gif][]\}

*清单2 src/tutorial/model/Book.java*

Book类有三个属性isbn,、title和price分别代表书籍的编号、名称和价格，其中编号用于唯一标识书籍（相当数据库中的主键）。

然后，我们再来看看Action类的代码：

![None.gif][] package  tutorial.action;  
![None.gif][]  
![None.gif][] import  java.util.Collection;  
![None.gif][]  
![None.gif][] import  tutorial.dao.BookDao;  
![None.gif][] import  tutorial.model.Book;  
![None.gif][]  
![None.gif][] import  com.opensymphony.xwork2.ActionSupport;  
![None.gif][]  
![ExpandedBlockStart.gif][] public  class  BookAction  extends  ActionSupport  \{  
![InBlock.gif][]privatestaticfinallong serialVersionUID =872316812305356L;  
![InBlock.gif][]  
![InBlock.gif][]private String isbn;  
![InBlock.gif][]private String\[\] isbns;  
![InBlock.gif][]private Book book;  
![InBlock.gif][]private Collection<Book> books;  
![InBlock.gif][]private BookDao dao = BookDao.getInstance();  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]public Book getBook() \{  
![InBlock.gif][]return book;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]publicvoid setBook(Book book) \{  
![InBlock.gif][]this.book = book;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]public String getIsbn() \{  
![InBlock.gif][]return isbn;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]publicvoid setIsbn(String isbn) \{  
![InBlock.gif][]this.isbn = isbn;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]public String\[\] getIsbns() \{  
![InBlock.gif][]return isbns;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]publicvoid setIsbns(String\[\] isbns) \{  
![InBlock.gif][]this.isbns = isbns;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]public Collection<Book> getBooks() \{  
![InBlock.gif][]return books;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]publicvoid setBooks(Collection<Book> books) \{  
![InBlock.gif][]this.books = books;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]public String load() \{  
![InBlock.gif][] book = dao.getBook(isbn);  
![InBlock.gif][]return SUCCESS;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]public String list() \{  
![InBlock.gif][] books = dao.getBooks();  
![InBlock.gif][]return SUCCESS;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]public String store() \{  
![InBlock.gif][] dao.storeBook(book);  
![InBlock.gif][]return SUCCESS;  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]  
![ExpandedSubBlockStart.gif][]public String remove() \{  
![ExpandedSubBlockStart.gif][]if(null!= isbn) \{  
![InBlock.gif][] dao.removeBook(isbn);  
![ExpandedSubBlockStart.gif][] \}else\{  
![InBlock.gif][] dao.removeBooks(isbns);  
![ExpandedSubBlockEnd.gif][] \}  
![InBlock.gif][]return SUCCESS;  
![ExpandedSubBlockEnd.gif][] \}  
![ExpandedBlockEnd.gif][]\}

*清单3 src/tutorial/action/BookAction.java*

BookAction类中属性isbn用于表示待编辑或删除的书籍的编号，属性isbns用于表示多个待删除的书籍的编号数组，属性book表示当前书籍，属性books则表示当前的书籍列表。BookAction有四个Action方法分别是load、list、store和remove，也即是CRUD都集中在BookAction中实现。

再下来是Action的配置代码：

<? xml version="1.0" encoding="UTF-8" ?>   
  
 <! DOCTYPE struts PUBLIC  
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"  
"http://struts.apache.org/dtds/struts-2.0.dtd" >   
  
 < struts >   
 < package  name ="Struts2\_CRUD\_DEMO"  extends ="struts-default"  namespace ="/Book" >   
 < action  name ="List"  class ="tutorial.action.BookAction"  method ="list" >   
 < result > List.jsp </ result >   
 </ action >   
 < action  name ="Edit"  class ="tutorial.action.BookAction"  method ="load" >   
 < result > Edit.jsp </ result >   
 </ action >   
 < action  name ="Store"  class ="tutorial.action.BookAction"  method ="store" >   
 < result  type ="redirect" > List.action </ result >   
 </ action >   
 < action  name ="Remove"  class ="tutorial.action.BookAction"  method ="remove" >   
 < result  type ="redirect" > List.action </ result >   
 </ action >   
 </ package >   
 </ struts >

*清单4 src/struts.xml*

以上的配置中，我使用了四个Action定义。它们都在“/Book”名值空间内。这样我就可以分别通过“http://localhost:8080/Struts2\_CRUD/Book/List.action”、“http://localhost:8080/Struts2\_CRUD/Book/Edit.action”、“http://localhost:8080/Struts2\_CRUD/Book/Store.action”和“http://localhost:8080/Struts2\_CRUD/Book/Remove.action”来调用BookAction的四个Action方法进行CRUD操作。当然，这只是个人喜好，你大可以只定义一个Action（假设其名称为“Book”），之后通过“http://localhost:8080/Struts2\_CRUD/Book!list.action”的方式来访问，详细做法请参考《[Struts 2.0的Action讲解][Struts 2.0_Action]》。另外，我由于希望在完成编辑或删除之后回到列表页，所以使用类型为redirect（重定向）的result。

下面是列表页面的代码：

<% @ page language = " java "  contentType = " text/html; charset=utf-8 "  pageEncoding = " utf-8 "  %>   
 <% @ taglib prefix = " s "  uri = " /struts-tags "  %>   
  
 <! DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" >   
 < html  xmlns ="http://www.w3.org/1999/xhtml" >   
 < head >   
 < title > Book List </ title >   
 < style  type ="text/css" >   
table  \{    
border :  1px solid black ;   
border-collapse :  collapse ;   
 \}   
  
table thead tr th  \{    
border :  1px solid black ;   
padding :  3px ;   
background-color :  \#cccccc ;   
 \}   
  
table tbody tr td  \{    
border :  1px solid black ;   
padding :  3px ;   
 \}   
 </ style >   
 </ head >   
 < body >   
 < h2 > Book List </ h2 >   
 < s:form  action ="Remove"  theme ="simple" >   
 < table  cellspacing ="0" >   
 < thead >   
 < tr >   
 < th > Select </ th >   
 < th > ISBN </ th >   
 < th > Title </ th >   
 < th > Price </ th >   
 < th > Operation </ th >   
 </ tr >   
 </ thead >   
 < tbody >   
 < s:iterator  value ="books" >   
 < tr >   
 < td >< input  type ="checkbox"  name ="isbns"  value ='<s:property  value ="isbn"  /> ' /> </ td >   
 < td >< s:property  value ="isbn"  /></ td >   
 < td >< s:property  value ="title"  /></ td >   
 < td > $ < s:property  value ="price"  /></ td >   
 < td >   
 < a  href ='<s:url  action ="Edit" >< s:param  name ="isbn"  value ="isbn"  /></ s:url > '>  
Edit  
 </ a >   
 &nbsp;   
 < a  href ='<s:url  action ="Remove" >< s:param  name ="isbn"  value ="isbn"  /></ s:url > '>  
Delete  
 </ a >   
 </ td >   
 </ tr >   
 </ s:iterator >   
 </ tbody >   
 </ table >   
 < s:submit  value ="Remove"  />< a  href ="Edit.jsp" > Add Book </ a >   
 </ s:form >   
 </ body >   
 </ html >

*清单5 WebContent/Book/List.jsp*

以上代码，值得注意的是在<s:form>标签，我设置了theme属性为“simple”，这样可以取消其默认的表格布局。之前，有些朋友问我“如果不希望提交按钮放在右边应该怎样做？”，上述做汗是答案之一。当然，更佳的做法自定义一个theme，并将其设为默认应用到整个站点，如此一来就可以得到统一的站点风格。我会在以后的文章中会对此作详细的描述。

编辑或添加书籍的页面代码如下：

*清单6 WebContent/Book/Edit.jsp*

如果book为null，则表明该页面用于添加书籍，反之则为编辑页面。

为了方便大家运行示例，我把web.xml的代码也贴出来，如下：

<? xml version="1.0" encoding="UTF-8" ?>   
 < web-app  id ="WebApp\_9"  version ="2.4"   
xmlns ="http://java.sun.com/xml/ns/j2ee"   
xmlns:xsi ="http://www.w3.org/2001/XMLSchema-instance"   
xsi:schemaLocation ="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app\_2\_4.xsd" >   
  
 < display-name > Struts 2 Fileupload </ display-name >   
  
 < filter >   
 < filter-name > struts2 </ filter-name >   
 < filter-class >   
org.apache.struts2.dispatcher.FilterDispatcher  
 </ filter-class >   
 </ filter >   
  
 < filter-mapping >   
 < filter-name > struts2 </ filter-name >   
 < url-pattern > /\* </ url-pattern >   
 </ filter-mapping >   
  
 < welcome-file-list >   
 < welcome-file > index.html </ welcome-file >   
 </ welcome-file-list >   
  
 </ web-app >

*清单7 WebContent/WEB-INF/web.xml*

大功告成，下面发布运行应用程序，在浏览器中键入：[http://localhost:8080/Struts2\_CRUD/Book/List.action][http_localhost_8080_Struts2_CRUD_Book_List.action]，出现如下图所示页面：

![r_img1.gif][]  
*清单8 列表页面*

点击“Add Book”，出现如下图所示页面：

![r_img2.gif][]  
*清单9 添加书籍页面*

后退回到列表页面，点击“Edit”，出现如下图所示页面：

![r_img3.gif][]  
*清单10 编辑书籍页面*

[None.gif]: /images/20220824/8e3530af283641f49cc4e3508fa50657.png
[ExpandedBlockStart.gif]: /images/20220824/3d953d78d0754bb497bafc48d272160d.png
[InBlock.gif]: /images/20220824/ff1090a6f6484e039ba1c90592a49655.png
[ExpandedSubBlockStart.gif]: /images/20220824/a04aa4c900dc499d923424c2749e9f59.png
[ExpandedSubBlockEnd.gif]: /images/20220824/95ef78da81eb4e768851c49ee440dcea.png
[ExpandedBlockEnd.gif]: /images/20220824/26dbb19079ac4e9b86e5d52d07383e90.png
[Struts 2.0_Action]: http://www.blogjava.net/max/archive/2006/10/25/77157.aspx
[http_localhost_8080_Struts2_CRUD_Book_List.action]: http://localhost:8080/Struts2_CRUD/Book/List.action
[r_img1.gif]: /images/20220824/a8b6640bfd3f485c8336ff893c59e94b.png
[r_img2.gif]: /images/20220824/dea1b67bffa14093be036528f9028903.png
[r_img3.gif]: /images/20220824/84afbf865f8349b695c838f50cc8fcc6.png