hibernate多对多 多对多
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<td width=87%>您要打印的文件是：<font color="#CC0000">Hibernate多对多示例</font>
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<p align="center"><strong><font size="3">Hibernate多对多示例</font></strong><br>
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作者：佚名 转贴自：http://www.http://xuehongliang.itpub.net.com/blog/ 点击数：1696</p>
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<td><P><FONT face=Arial>假設現在有User與Server兩個類別，一個User可以被授權使用多台Server，而在Server上也記錄授權使用它的使用者，就User與Server兩者而言即使多對多的關係。 </FONT></P>
<P><FONT face=Arial>在程式設計時，基本上是不建議直接在User與Server之間建立多對多關係，這會使得User與Server相互依賴，通常會透過一個中介類別來維護兩者之間的多對多關係，避免兩者的相互依賴。 </FONT></P>
<P><FONT face=Arial>如果一定要直接建立User與Server之間的多對多關係，Hibernate也是支援的，基本上只要您瞭解之前介紹的幾個實體映射，建立多對多關聯在配置上並不困難。 </FONT></P>
<P><FONT face=Arial>先看一下我們設計的User與Server類別： </FONT></P>
<DIV class=code_title>java 代码</DIV>
<DIV class=dp-highlighter>
<DIV class=bar></DIV>
<OL class=dp-j>
<LI class=alt><SPAN><SPAN class=keyword>package</SPAN><SPAN> onlyfun.caterpillar; </SPAN></SPAN>
<LI><SPAN></SPAN>
<LI class=alt><SPAN class=keyword>import</SPAN><SPAN> java.util.*; </SPAN>
<LI><SPAN></SPAN>
<LI class=alt><SPAN class=keyword>public</SPAN><SPAN> </SPAN><SPAN class=keyword>class</SPAN><SPAN> User { </SPAN>
<LI><SPAN></SPAN><SPAN class=keyword>private</SPAN><SPAN> </SPAN><SPAN class=keyword>long</SPAN><SPAN> id; </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=keyword>private</SPAN><SPAN> String name; </SPAN>
<LI><SPAN></SPAN><SPAN class=keyword>private</SPAN><SPAN> Set servers = </SPAN><SPAN class=keyword>new</SPAN><SPAN> HashSet(); </SPAN>
<LI class=alt><SPAN></SPAN>
<LI><SPAN></SPAN><SPAN class=keyword>public</SPAN><SPAN> </SPAN><SPAN class=keyword>long</SPAN><SPAN> getId() { </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=keyword>return</SPAN><SPAN> id; </SPAN>
<LI><SPAN>} </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=keyword>public</SPAN><SPAN> </SPAN><SPAN class=keyword>void</SPAN><SPAN> setId(</SPAN><SPAN class=keyword>long</SPAN><SPAN> id) { </SPAN>
<LI><SPAN></SPAN><SPAN class=keyword>this</SPAN><SPAN>.id = id; </SPAN>
<LI class=alt><SPAN>} </SPAN>
<LI><SPAN></SPAN><SPAN class=keyword>public</SPAN><SPAN> String getName() { </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=keyword>return</SPAN><SPAN> name; </SPAN>
<LI><SPAN>} </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=keyword>public</SPAN><SPAN> </SPAN><SPAN class=keyword>void</SPAN><SPAN> setName(String name) { </SPAN>
<LI><SPAN></SPAN><SPAN class=keyword>this</SPAN><SPAN>.name = name; </SPAN>
<LI class=alt><SPAN>} </SPAN>
<LI><SPAN></SPAN><SPAN class=keyword>public</SPAN><SPAN> Set getServers() { </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=keyword>return</SPAN><SPAN> servers; </SPAN>
<LI><SPAN>} </SPAN>
<LI class=alt><SPAN></SPAN>
<LI><SPAN></SPAN><SPAN class=keyword>public</SPAN><SPAN> </SPAN><SPAN class=keyword>void</SPAN><SPAN> setServers(Set servers) { </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=keyword>this</SPAN><SPAN>.servers = servers; </SPAN>
<LI><SPAN>} </SPAN>
<LI class=alt><SPAN>} </SPAN></LI></OL></DIV>
<DIV class=code_title>java 代码</DIV>
<DIV class=dp-highlighter>
<DIV class=bar></DIV>
<OL class=dp-j>
<LI class=alt><SPAN><SPAN class=keyword>package</SPAN><SPAN> onlyfun.caterpillar; </SPAN></SPAN>
<LI><SPAN></SPAN>
<LI class=alt><SPAN class=keyword>import</SPAN><SPAN> java.util.*; </SPAN>
<LI><SPAN></SPAN>
<LI class=alt><SPAN class=keyword>public</SPAN><SPAN> </SPAN><SPAN class=keyword>class</SPAN><SPAN> Server { </SPAN>
<LI><SPAN></SPAN><SPAN class=keyword>private</SPAN><SPAN> </SPAN><SPAN class=keyword>long</SPAN><SPAN> id; </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=keyword>private</SPAN><SPAN> String address; </SPAN>
<LI><SPAN></SPAN><SPAN class=keyword>private</SPAN><SPAN> Set users = </SPAN><SPAN class=keyword>new</SPAN><SPAN> HashSet(); </SPAN>
<LI class=alt><SPAN></SPAN>
<LI><SPAN></SPAN><SPAN class=keyword>public</SPAN><SPAN> </SPAN><SPAN class=keyword>long</SPAN><SPAN> getId() { </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=keyword>return</SPAN><SPAN> id; </SPAN>
<LI><SPAN>} </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=keyword>public</SPAN><SPAN> </SPAN><SPAN class=keyword>void</SPAN><SPAN> setId(</SPAN><SPAN class=keyword>long</SPAN><SPAN> id) { </SPAN>
<LI><SPAN></SPAN><SPAN class=keyword>this</SPAN><SPAN>.id = id; </SPAN>
<LI class=alt><SPAN>} </SPAN>
<LI><SPAN></SPAN><SPAN class=keyword>public</SPAN><SPAN> String getAddress() { </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=keyword>return</SPAN><SPAN> address; </SPAN>
<LI><SPAN>} </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=keyword>public</SPAN><SPAN> </SPAN><SPAN class=keyword>void</SPAN><SPAN> setAddress(String address) { </SPAN>
<LI><SPAN></SPAN><SPAN class=keyword>this</SPAN><SPAN>.address = address; </SPAN>
<LI class=alt><SPAN>} </SPAN>
<LI><SPAN></SPAN><SPAN class=keyword>public</SPAN><SPAN> Set getUsers() { </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=keyword>return</SPAN><SPAN> users; </SPAN>
<LI><SPAN>} </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=keyword>public</SPAN><SPAN> </SPAN><SPAN class=keyword>void</SPAN><SPAN> setUsers(Set users) { </SPAN>
<LI><SPAN></SPAN><SPAN class=keyword>this</SPAN><SPAN>.users = users; </SPAN>
<LI class=alt><SPAN>} </SPAN>
<LI><SPAN>} </SPAN></LI></OL></DIV>
<P><FONT face=Arial>這邊各使用HashSet來保存彼此的關係，在多對多關係映射上，我們可以建立單向或雙向關係，這邊直接介紹雙向關係映射，並藉由設定inverse="true"，將關係的維護交由其中一方來維護，這麼作的結果，在原始碼的撰寫上，也比較符合Java的物件關係維護，也就是雙方都要設置至對方的參考。 </FONT></P>
<P><FONT face=Arial>首先來看看User.hbm.xml： </FONT></P>
<DIV class=code_title>xml 代码</DIV>
<DIV class=dp-highlighter>
<DIV class=bar></DIV>
<OL class=dp-xml>
<LI class=alt><SPAN><SPAN class=tag><SPAN class=tag-name>xml</SPAN><SPAN> </SPAN><SPAN class=attribute>version</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"1.0"</SPAN><SPAN class=tag>?></SPAN><SPAN> </SPAN></SPAN></SPAN>
<LI><SPAN></SPAN>
<LI class=alt><SPAN>PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" </SPAN>
<LI><SPAN>"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd"</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN>
<LI class=alt><SPAN></SPAN>
<LI><SPAN class=tag><</SPAN><SPAN class=tag-name>hibernate-mapping</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN>
<LI class=alt><SPAN></SPAN>
<LI><SPAN></SPAN><SPAN class=tag><</SPAN><SPAN class=tag-name>class</SPAN><SPAN> </SPAN><SPAN class=attribute>name</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"onlyfun.caterpillar.User"</SPAN><SPAN> </SPAN><SPAN class=attribute>table</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"USER"</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN>
<LI class=alt><SPAN></SPAN>
<LI><SPAN></SPAN><SPAN class=tag><</SPAN><SPAN class=tag-name>id</SPAN><SPAN> </SPAN><SPAN class=attribute>name</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"id"</SPAN><SPAN> </SPAN><SPAN class=attribute>column</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"USER_ID"</SPAN><SPAN> </SPAN><SPAN class=attribute>unsaved-value</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"0"</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=tag><</SPAN><SPAN class=tag-name>generator</SPAN><SPAN> </SPAN><SPAN class=attribute>class</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"increment"</SPAN><SPAN class=tag>/></SPAN><SPAN> </SPAN>
<LI><SPAN></SPAN><SPAN class=tag><SPAN class=tag-name>id</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN></SPAN>
<LI class=alt><SPAN></SPAN>
<LI><SPAN></SPAN><SPAN class=tag><</SPAN><SPAN class=tag-name>property</SPAN><SPAN> </SPAN><SPAN class=attribute>name</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"name"</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=tag><</SPAN><SPAN class=tag-name>column</SPAN><SPAN> </SPAN><SPAN class=attribute>name</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"NAME"</SPAN><SPAN> </SPAN><SPAN class=attribute>length</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"16"</SPAN><SPAN> </SPAN><SPAN class=attribute>not-null</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"true"</SPAN><SPAN class=tag>/></SPAN><SPAN> </SPAN>
<LI><SPAN></SPAN><SPAN class=tag><SPAN class=tag-name>property</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN></SPAN>
<LI class=alt><SPAN></SPAN>
<LI><SPAN></SPAN><SPAN class=tag><</SPAN><SPAN class=tag-name>set</SPAN><SPAN> </SPAN><SPAN class=attribute>name</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"servers"</SPAN><SPAN> </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=attribute>table</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"USER_SERVER"</SPAN><SPAN> </SPAN>
<LI><SPAN></SPAN><SPAN class=attribute>cascade</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"save-update"</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN>
<LI class=alt><SPAN></SPAN>
<LI><SPAN></SPAN><SPAN class=tag><</SPAN><SPAN class=tag-name>key</SPAN><SPAN> </SPAN><SPAN class=attribute>column</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"USER_ID"</SPAN><SPAN class=tag>/></SPAN><SPAN> </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=tag><</SPAN><SPAN class=tag-name>many-to-many</SPAN><SPAN> </SPAN><SPAN class=attribute>class</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"onlyfun.caterpillar.Server"</SPAN><SPAN> </SPAN>
<LI><SPAN></SPAN><SPAN class=attribute>column</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"SERVER_ID"</SPAN><SPAN class=tag>/></SPAN><SPAN> </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=tag><SPAN class=tag-name>set</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN></SPAN>
<LI><SPAN></SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=tag><SPAN class=tag-name>class</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN></SPAN>
<LI><SPAN></SPAN>
<LI class=alt><SPAN class=tag><SPAN class=tag-name>hibernate-mapping</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN></SPAN></LI></OL></DIV>
<P><FONT face=Arial>在資料庫中，資料表之間的多對多關係是透過一個中介的資料表來完成，例如在這個例子中，USER資料表與USER_SERVER資料表是一對多，而USER_SERVER對SERVER是多對一，從而完成USER至SERVER的多對多關係，在USER_SERVER資料表中，將會有USER_ID與SERVER_ID共同作為主鍵，USER_ID作為一個至USER的外鍵參考，而SERVER_ID作為一個至SERVER的外鍵參考。 </FONT></P>
<P><FONT face=Arial>來看看Server.hbm.xml映射文件：</FONT></P>
<DIV class=code_title>xml 代码</DIV>
<DIV class=dp-highlighter>
<DIV class=bar></DIV>
<OL class=dp-xml>
<LI class=alt><SPAN><SPAN class=tag><SPAN class=tag-name>xml</SPAN><SPAN> </SPAN><SPAN class=attribute>version</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"1.0"</SPAN><SPAN class=tag>?></SPAN><SPAN> </SPAN></SPAN></SPAN>
<LI><SPAN></SPAN>
<LI class=alt><SPAN>PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" </SPAN>
<LI><SPAN>"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd"</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN>
<LI class=alt><SPAN></SPAN>
<LI><SPAN class=tag><</SPAN><SPAN class=tag-name>hibernate-mapping</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN>
<LI class=alt><SPAN></SPAN>
<LI><SPAN></SPAN><SPAN class=tag><</SPAN><SPAN class=tag-name>class</SPAN><SPAN> </SPAN><SPAN class=attribute>name</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"onlyfun.caterpillar.Server"</SPAN><SPAN> </SPAN><SPAN class=attribute>table</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"SERVER"</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN>
<LI class=alt><SPAN></SPAN>
<LI><SPAN></SPAN><SPAN class=tag><</SPAN><SPAN class=tag-name>id</SPAN><SPAN> </SPAN><SPAN class=attribute>name</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"id"</SPAN><SPAN> </SPAN><SPAN class=attribute>column</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"SERVER_ID"</SPAN><SPAN> </SPAN><SPAN class=attribute>unsaved-value</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"0"</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=tag><</SPAN><SPAN class=tag-name>generator</SPAN><SPAN> </SPAN><SPAN class=attribute>class</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"increment"</SPAN><SPAN class=tag>/></SPAN><SPAN> </SPAN>
<LI><SPAN></SPAN><SPAN class=tag><SPAN class=tag-name>id</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN></SPAN>
<LI class=alt><SPAN></SPAN>
<LI><SPAN></SPAN><SPAN class=tag><</SPAN><SPAN class=tag-name>property</SPAN><SPAN> </SPAN><SPAN class=attribute>name</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"address"</SPAN><SPAN> </SPAN><SPAN class=attribute>type</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"string"</SPAN><SPAN class=tag>/></SPAN><SPAN> </SPAN>
<LI class=alt><SPAN></SPAN>
<LI><SPAN></SPAN><SPAN class=tag><</SPAN><SPAN class=tag-name>set</SPAN><SPAN> </SPAN><SPAN class=attribute>name</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"users"</SPAN><SPAN> </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=attribute>table</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"USER_SERVER"</SPAN><SPAN> </SPAN>
<LI><SPAN></SPAN><SPAN class=attribute>inverse</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"true"</SPAN><SPAN> </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=attribute>cascade</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"save-update"</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN>
<LI><SPAN></SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=tag><</SPAN><SPAN class=tag-name>key</SPAN><SPAN> </SPAN><SPAN class=attribute>column</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"SERVER_ID"</SPAN><SPAN class=tag>/></SPAN><SPAN> </SPAN>
<LI><SPAN></SPAN><SPAN class=tag><</SPAN><SPAN class=tag-name>many-to-many</SPAN><SPAN> </SPAN><SPAN class=attribute>class</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"onlyfun.caterpillar.User"</SPAN><SPAN> </SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=attribute>column</SPAN><SPAN>=</SPAN><SPAN class=attribute-value>"USER_ID"</SPAN><SPAN class=tag>/></SPAN><SPAN> </SPAN>
<LI><SPAN></SPAN><SPAN class=tag><SPAN class=tag-name>set</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN></SPAN>
<LI class=alt><SPAN></SPAN><SPAN class=tag><SPAN class=tag-name>class</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN></SPAN>
<LI><SPAN></SPAN>
<LI class=alt><SPAN class=tag><SPAN class=tag-name>hibernate-mapping</SPAN><SPAN class=tag>></SPAN><SPAN> </SPAN></SPAN></LI></OL></DIV>
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