Hibernate关联关系可分为单向关联和双向关联两大类。单向关联可以分为一对一、一对多、多对一和多对多4种关联方式,而多向关联可以分为一对一、一对多和多对多3种关联方式。 Hibernate连接管理类HibernateUtil.Java public class HibernateUtil { private st
Hibernate关联关系可分为单向关联和双向关联两大类。单向关联可以分为一对一、一对多、多对一和多对多4种关联方式,而多向关联可以分为一对一、一对多和多对多3种关联方式。
Hibernate连接管理类HibernateUtil.Java
<code class=" hljs cs"><span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> HibernateUtil { <span class="hljs-keyword">private</span> <span class="hljs-keyword">static</span> SessionFactory sessionFactory; <span class="hljs-keyword">private</span> <span class="hljs-keyword">static</span> final ThreadLocal<Session> threadLocal = <span class="hljs-keyword">new</span> ThreadLocal<Session>(); <span class="hljs-keyword">static</span>{ <span class="hljs-keyword">try</span>{ Configuration cfg = <span class="hljs-keyword">new</span> Configuration().configure(); sessionFactory = cfg.buildSessionFactory(); }<span class="hljs-keyword">catch</span>(Throwable ex){ <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> ExceptionInInitializerError(ex); } } <span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> SessionFactory <span class="hljs-title">getSessionFactory</span>(){ <span class="hljs-keyword">return</span> sessionFactory; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> Session <span class="hljs-title">getSession</span>() throws HibernateException{ Session session = (Session)threadLocal.<span class="hljs-keyword">get</span>(); <span class="hljs-keyword">if</span>(session == <span class="hljs-keyword">null</span> || !session.isOpen()){ session = (sessionFactory != <span class="hljs-keyword">null</span>)?sessionFactory.openSession():<span class="hljs-keyword">null</span>; threadLocal.<span class="hljs-keyword">set</span>(session); } <span class="hljs-keyword">return</span> session; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">closeSession</span>() throws HibernateException{ Session session = (Session)threadLocal.<span class="hljs-keyword">get</span>(); threadLocal.<span class="hljs-keyword">set</span>(<span class="hljs-keyword">null</span>); <span class="hljs-keyword">if</span>(session != <span class="hljs-keyword">null</span>){ session.close(); } } <span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">shutdown</span>(){ getSessionFactory().close(); } }</code>
1.双向的一对一关联
(1)通过主键关联
通过主键关联的双向一对一映射,在需要一方的配置文件中将主键生成策略配置成foreign,即表示需要根据另一方的主键来生成自己的主键,而该实体本身不具有自己的主键生成策略。
示例:
实体类:
User.java
<code class=" hljs cs"><span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> User { <span class="hljs-keyword">private</span> <span class="hljs-keyword">int</span> userid; <span class="hljs-keyword">private</span> String name; <span class="hljs-keyword">private</span> String password; <span class="hljs-keyword">private</span> Address address; <span class="hljs-keyword">public</span> <span class="hljs-keyword">int</span> <span class="hljs-title">getUserid</span>() { <span class="hljs-keyword">return</span> userid; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setUserid</span>(<span class="hljs-keyword">int</span> userid) { <span class="hljs-keyword">this</span>.userid = userid; } <span class="hljs-keyword">public</span> String <span class="hljs-title">getName</span>() { <span class="hljs-keyword">return</span> name; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setName</span>(String name) { <span class="hljs-keyword">this</span>.name = name; } <span class="hljs-keyword">public</span> String <span class="hljs-title">getPassword</span>() { <span class="hljs-keyword">return</span> password; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setPassword</span>(String password) { <span class="hljs-keyword">this</span>.password = password; } <span class="hljs-keyword">public</span> Address <span class="hljs-title">getAddress</span>() { <span class="hljs-keyword">return</span> address; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setAddress</span>(Address address) { <span class="hljs-keyword">this</span>.address = address; } }</code>
Address.java
<code class=" hljs cs"><span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> Address { <span class="hljs-keyword">private</span> <span class="hljs-keyword">int</span> addressid; <span class="hljs-keyword">private</span> String addressinfo; <span class="hljs-keyword">private</span> User user; <span class="hljs-keyword">public</span> <span class="hljs-keyword">int</span> <span class="hljs-title">getAddressid</span>() { <span class="hljs-keyword">return</span> addressid; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setAddressid</span>(<span class="hljs-keyword">int</span> addressid) { <span class="hljs-keyword">this</span>.addressid = addressid; } <span class="hljs-keyword">public</span> String <span class="hljs-title">getAddressinfo</span>() { <span class="hljs-keyword">return</span> addressinfo; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setAddressinfo</span>(String addressinfo) { <span class="hljs-keyword">this</span>.addressinfo = addressinfo; } <span class="hljs-keyword">public</span> User <span class="hljs-title">getUser</span>() { <span class="hljs-keyword">return</span> user; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setUser</span>(User user) { <span class="hljs-keyword">this</span>.user = user; } }</code>
表结构:
User表
Address表
配置文件:
Use.hbm.xml
<code class=" hljs applescript"><hibernate-mapping> <<span class="hljs-type">class</span> <span class="hljs-property">name</span>=<span class="hljs-string">"com.entity.User"</span> table=<span class="hljs-string">"user"</span>> <<span class="hljs-property">id</span> <span class="hljs-property">name</span>=<span class="hljs-string">"userid"</span> type=<span class="hljs-string">"java.lang.Integer"</span> column=<span class="hljs-string">"userid"</span>> <generator <span class="hljs-type">class</span>=<span class="hljs-string">"identity"</span>/> </<span class="hljs-property">id</span>> <<span class="hljs-keyword">property</span> <span class="hljs-property">name</span>=<span class="hljs-string">"name"</span> type=<span class="hljs-string">"java.lang.String"</span> column=<span class="hljs-string">"name"</span>> </<span class="hljs-keyword">property</span>> <<span class="hljs-keyword">property</span> <span class="hljs-property">name</span>=<span class="hljs-string">"password"</span> type=<span class="hljs-string">"java.lang.String"</span> column=<span class="hljs-string">"password"</span>> </<span class="hljs-keyword">property</span>> <one-<span class="hljs-keyword">to</span>-one <span class="hljs-property">name</span>=<span class="hljs-string">"address"</span> <span class="hljs-type">class</span>=<span class="hljs-string">"com.entity.Address"</span> cascade=<span class="hljs-string">"all"</span>/> </<span class="hljs-type">class</span>> </hibernate-mapping></code>
Address.hbm.xml
<code class=" hljs applescript"><hibernate-mapping> <<span class="hljs-type">class</span> <span class="hljs-property">name</span>=<span class="hljs-string">"com.entity.Address"</span> table=<span class="hljs-string">"address"<span>> <<span class="hljs-property">id</span> <span class="hljs-property">name</span>=<span class="hljs-string">"addressid"</span> type=<span class="hljs-string">"java.lang.Integer"</span> column=<span class="hljs-string">"addressid"</span>> <generator <span class="hljs-type">class</span>=<span class="hljs-string">"foreign"</span>> <param <span class="hljs-property">name</span>=<span class="hljs-string">"property"</span>>user</param> </generator> </<span class="hljs-property">id</span>> <<span class="hljs-keyword">property</span> <span class="hljs-property">name</span>=<span class="hljs-string">"addressinfo"</span> type=<span class="hljs-string">"java.lang.String"</span> column=<span class="hljs-string">"addressinfo"</span>> </<span class="hljs-keyword">property</span>> <one-<span class="hljs-keyword">to</span>-one <span class="hljs-property">name</span>=<span class="hljs-string">"user"</span> <span class="hljs-type">class</span>=<span class="hljs-string">"com.entity.User"</span> constrained=<span class="hljs-string">"true"</span>/> </<span class="hljs-type">class</span>> </hibernate-mapping></code>
测试类Test.java
<code class=" hljs cs"><span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> Test { <span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span>(String[] args){ Session session = HibernateUtil.getSession(); Transaction tx = session.beginTransaction(); User u = <span class="hljs-keyword">new</span> User(); u.setName(<span class="hljs-string">"sbw"</span>); u.setPassword(<span class="hljs-string">"123"</span>); Address a = <span class="hljs-keyword">new</span> Address(); a.setAddressinfo(<span class="hljs-string">"heu"</span>); a.setUser(u); u.setAddress(a); session.save(u); session.save(a); tx.commit(); HibernateUtil.closeSession(); } }</code>
测试结果:
(2)通过外键关联
通过外键关联的双向一对一映射,外键可以放在任意一方。在存放外键一方的映射文件中,需要添加many-to-one元素,并为该元素添加unique=“true”属性。而另一方的配置文件中要添加one-to-one元素,并使用其name属性来指定关联属性名。此时,存放外键的一方对应的数据表为从表,而另一方对应的数据表变为主表。
实体类与通过主键关联相同。
表结构:
user表
address表
配置文件:
User.hbm.xml
<code class=" hljs applescript"><hibernate-mapping> <<span class="hljs-type">class</span> <span class="hljs-property">name</span>=<span class="hljs-string">"com.entity.User"</span> table=<span class="hljs-string">"user"</span>> <<span class="hljs-property">id</span> <span class="hljs-property">name</span>=<span class="hljs-string">"userid"</span> type=<span class="hljs-string">"java.lang.Integer"</span> column=<span class="hljs-string">"userid"</span>> <generator <span class="hljs-type">class</span>=<span class="hljs-string">"identity"</span>/> </<span class="hljs-property">id</span>> <<span class="hljs-keyword">property</span> <span class="hljs-property">name</span>=<span class="hljs-string">"name"</span> type=<span class="hljs-string">"java.lang.String"</span> column=<span class="hljs-string">"name"</span>> </<span class="hljs-keyword">property</span>> <<span class="hljs-keyword">property</span> <span class="hljs-property">name</span>=<span class="hljs-string">"password"</span> type=<span class="hljs-string">"java.lang.String"</span> column=<span class="hljs-string">"password"</span>> </<span class="hljs-keyword">property</span>> <one-<span class="hljs-keyword">to</span>-one <span class="hljs-property">name</span>=<span class="hljs-string">"address"</span> cascade=<span class="hljs-string">"all"</span>/> </<span class="hljs-type">class</span>> </hibernate-mapping></code>
Address.hbm.xml
<code class=" hljs applescript"><hibernate-mapping> <<span class="hljs-type">class</span> <span class="hljs-property">name</span>=<span class="hljs-string">"com.entity.Address"</span> table=<span class="hljs-string">"address"</span>> <<span class="hljs-property">id</span> <span class="hljs-property">name</span>=<span class="hljs-string">"addressid"</span> type=<span class="hljs-string">"java.lang.Integer"</span> column=<span class="hljs-string">"addressid"</span>> <generator <span class="hljs-type">class</span>=<span class="hljs-string">"identity"</span>> </generator> </<span class="hljs-property">id</span>> <<span class="hljs-keyword">property</span> <span class="hljs-property">name</span>=<span class="hljs-string">"addressinfo"</span> type=<span class="hljs-string">"java.lang.String"</span> column=<span class="hljs-string">"addressinfo"</span>> </<span class="hljs-keyword">property</span>> <many-<span class="hljs-keyword">to</span>-one <span class="hljs-property">name</span>=<span class="hljs-string">"user"</span> <span class="hljs-type">class</span>=<span class="hljs-string">"com.entity.User"</span> unique=<span class="hljs-string">"true"</span>> <column <span class="hljs-property">name</span>=<span class="hljs-string">"userid"</span>/> </many-<span class="hljs-keyword">to</span>-one> </<span class="hljs-type">class</span>> </hibernate-mapping></code>
测试类与通过主键关联一样
测试结果:
2.双向的一对多关联(与双向多对一完全相同)
双向的一对多关联在“多”的一方要增加新属性以引用关联实体,在“一”的一方则增加集合属性,该集合中包含“多”的一方的关联实体。
实体类:
User.java
<code class=" hljs cs"><span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> User { <span class="hljs-keyword">private</span> <span class="hljs-keyword">int</span> userid; <span class="hljs-keyword">private</span> String name; <span class="hljs-keyword">private</span> String password; <span class="hljs-keyword">private</span> Set<Address> address = <span class="hljs-keyword">new</span> HashSet<Address>(); <span class="hljs-keyword">public</span> <span class="hljs-keyword">int</span> <span class="hljs-title">getUserid</span>() { <span class="hljs-keyword">return</span> userid; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setUserid</span>(<span class="hljs-keyword">int</span> userid) { <span class="hljs-keyword">this</span>.userid = userid; } <span class="hljs-keyword">public</span> String <span class="hljs-title">getName</span>() { <span class="hljs-keyword">return</span> name; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setName</span>(String name) { <span class="hljs-keyword">this</span>.name = name; } <span class="hljs-keyword">public</span> String <span class="hljs-title">getPassword</span>() { <span class="hljs-keyword">return</span> password; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setPassword</span>(String password) { <span class="hljs-keyword">this</span>.password = password; } <span class="hljs-keyword">public</span> Set<Address> <span class="hljs-title">getAddress</span>() { <span class="hljs-keyword">return</span> address; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setAddress</span>(Set<Address> address) { <span class="hljs-keyword">this</span>.address = address; } }</code>
Address.java
<code class=" hljs cs"><span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> Address { <span class="hljs-keyword">private</span> <span class="hljs-keyword">int</span> addressid; <span class="hljs-keyword">private</span> String addressinfo; <span class="hljs-keyword">private</span> User user; <span class="hljs-keyword">public</span> <span class="hljs-keyword">int</span> <span class="hljs-title">getAddressid</span>() { <span class="hljs-keyword">return</span> addressid; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setAddressid</span>(<span class="hljs-keyword">int</span> addressid) { <span class="hljs-keyword">this</span>.addressid = addressid; } <span class="hljs-keyword">public</span> String <span class="hljs-title">getAddressinfo</span>() { <span class="hljs-keyword">return</span> addressinfo; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setAddressinfo</span>(String addressinfo) { <span class="hljs-keyword">this</span>.addressinfo = addressinfo; } <span class="hljs-keyword">public</span> User <span class="hljs-title">getUser</span>() { <span class="hljs-keyword">return</span> user; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setUser</span>(User user) { <span class="hljs-keyword">this</span>.user = user; } }</code>
表结构:
user表
address表
配置文件
User.hbm.xml
<code class=" hljs applescript"><hibernate-mapping> <<span class="hljs-type">class</span> <span class="hljs-property">name</span>=<span class="hljs-string">"com.entity.User"</span> table=<span class="hljs-string">"user"</span>> <<span class="hljs-property">id</span> <span class="hljs-property">name</span>=<span class="hljs-string">"userid"</span> type=<span class="hljs-string">"java.lang.Integer"</span> column=<span class="hljs-string">"userid"</span>> <generator <span class="hljs-type">class</span>=<span class="hljs-string">"identity"</span>/> </<span class="hljs-property">id</span>> <<span class="hljs-keyword">property</span> <span class="hljs-property">name</span>=<span class="hljs-string">"name"</span> type=<span class="hljs-string">"java.lang.String"</span> column=<span class="hljs-string">"name"</span>> </<span class="hljs-keyword">property</span>> <<span class="hljs-keyword">property</span> <span class="hljs-property">name</span>=<span class="hljs-string">"password"</span> type=<span class="hljs-string">"java.lang.String"</span> column=<span class="hljs-string">"password"</span>> </<span class="hljs-keyword">property</span>> <<span class="hljs-keyword">set</span> <span class="hljs-property">name</span>=<span class="hljs-string">"address"</span> table=<span class="hljs-string">"address"</span> inverse=<span class="hljs-string">"true"</span> lazy=<span class="hljs-string">"true"</span>> <key> <column <span class="hljs-property">name</span>=<span class="hljs-string">"userid"</span>/> </key> <one-<span class="hljs-keyword">to</span>-many <span class="hljs-type">class</span>=<span class="hljs-string">"com.entity.Address"</span>/> </<span class="hljs-keyword">set</span>> </<span class="hljs-type">class</span>> </hibernate-mapping></code>
Address.hbm.xml
<code class=" hljs applescript"><hibernate-mapping> <<span class="hljs-type">class</span> <span class="hljs-property">name</span>=<span class="hljs-string">"com.entity.Address"</span> table=<span class="hljs-string">"address"</span>> <<span class="hljs-property">id</span> <span class="hljs-property">name</span>=<span class="hljs-string">"addressid"</span> type=<span class="hljs-string">"java.lang.Integer"</span> column=<span class="hljs-string">"addressid"</span>> <generator <span class="hljs-type">class</span>=<span class="hljs-string">"identity"</span>> </generator> </<span class="hljs-property">id</span>> <<span class="hljs-keyword">property</span> <span class="hljs-property">name</span>=<span class="hljs-string">"addressinfo"</span> type=<span class="hljs-string">"java.lang.String"</span> column=<span class="hljs-string">"addressinfo"</span>> </<span class="hljs-keyword">property</span>> <many-<span class="hljs-keyword">to</span>-one <span class="hljs-property">name</span>=<span class="hljs-string">"user"</span> <span class="hljs-type">class</span>=<span class="hljs-string">"com.entity.User"</span> unique=<span class="hljs-string">"true"</span>> <column <span class="hljs-property">name</span>=<span class="hljs-string">"userid"</span>/> </many-<span class="hljs-keyword">to</span>-one> </<span class="hljs-type">class</span>> </hibernate-mapping></code>
测试类Test.java
<code class=" hljs avrasm">public class Test { public static void main(String[] args){ Session session = HibernateUtil<span class="hljs-preprocessor">.getSession</span>()<span class="hljs-comment">;</span> Transaction tx = session<span class="hljs-preprocessor">.beginTransaction</span>()<span class="hljs-comment">;</span> User u = new User()<span class="hljs-comment">;</span> u<span class="hljs-preprocessor">.setName</span>(<span class="hljs-string">"sbw"</span>)<span class="hljs-comment">;</span> u<span class="hljs-preprocessor">.setPassword</span>(<span class="hljs-string">"123"</span>)<span class="hljs-comment">; </span> Address a = new Address()<span class="hljs-comment">;</span> a<span class="hljs-preprocessor">.setAddressinfo</span>(<span class="hljs-string">"heu"</span>)<span class="hljs-comment">;</span> Address a1 = new Address()<span class="hljs-comment">;</span> a<span class="hljs-preprocessor">.setAddressinfo</span>(<span class="hljs-string">"hrb"</span>)<span class="hljs-comment">;</span> a<span class="hljs-preprocessor">.setUser</span>(u)<span class="hljs-comment">;</span> a1<span class="hljs-preprocessor">.setUser</span>(u)<span class="hljs-comment">;</span> u<span class="hljs-preprocessor">.getAddress</span>()<span class="hljs-preprocessor">.add</span>(a)<span class="hljs-comment">;</span> u<span class="hljs-preprocessor">.getAddress</span>()<span class="hljs-preprocessor">.add</span>(a1)<span class="hljs-comment">;</span> session<span class="hljs-preprocessor">.save</span>(a)<span class="hljs-comment">;</span> session<span class="hljs-preprocessor">.save</span>(a1)<span class="hljs-comment">;</span> session<span class="hljs-preprocessor">.save</span>(u)<span class="hljs-comment">;</span> tx<span class="hljs-preprocessor">.commit</span>()<span class="hljs-comment">;</span> HibernateUtil<span class="hljs-preprocessor">.closeSession</span>()<span class="hljs-comment">;</span> } }</code>
测试结果:
3.双向的多对多关联
在双向的多对多关联中,两端都要添加Set集合属性。要实现双向的多对多关联,必须使用中间表来实现两个实体间的关联关系。
示例:
实体类
User.java
<code class=" hljs cs"><span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> User { <span class="hljs-keyword">private</span> <span class="hljs-keyword">int</span> userid; <span class="hljs-keyword">private</span> String name; <span class="hljs-keyword">private</span> String password; <span class="hljs-keyword">private</span> Set<Address> address = <span class="hljs-keyword">new</span> HashSet<Address>(); <span class="hljs-keyword">public</span> <span class="hljs-keyword">int</span> <span class="hljs-title">getUserid</span>() { <span class="hljs-keyword">return</span> userid; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setUserid</span>(<span class="hljs-keyword">int</span> userid) { <span class="hljs-keyword">this</span>.userid = userid; } <span class="hljs-keyword">public</span> String <span class="hljs-title">getName</span>() { <span class="hljs-keyword">return</span> name; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setName</span>(String name) { <span class="hljs-keyword">this</span>.name = name; } <span class="hljs-keyword">public</span> String <span class="hljs-title">getPassword</span>() { <span class="hljs-keyword">return</span> password; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setPassword</span>(String password) { <span class="hljs-keyword">this</span>.password = password; } <span class="hljs-keyword">public</span> Set<Address> <span class="hljs-title">getAddress</span>() { <span class="hljs-keyword">return</span> address; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setAddress</span>(Set<Address> address) { <span class="hljs-keyword">this</span>.address = address; } }</code>
Address.java
<code class=" hljs cs"><span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> Address { <span class="hljs-keyword">private</span> <span class="hljs-keyword">int</span> addressid; <span class="hljs-keyword">private</span> String addressinfo; <span class="hljs-keyword">private</span> Set<User> user = <span class="hljs-keyword">new</span> HashSet<User>(); <span class="hljs-keyword">public</span> <span class="hljs-keyword">int</span> <span class="hljs-title">getAddressid</span>() { <span class="hljs-keyword">return</span> addressid; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setAddressid</span>(<span class="hljs-keyword">int</span> addressid) { <span class="hljs-keyword">this</span>.addressid = addressid; } <span class="hljs-keyword">public</span> String <span class="hljs-title">getAddressinfo</span>() { <span class="hljs-keyword">return</span> addressinfo; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setAddressinfo</span>(String addressinfo) { <span class="hljs-keyword">this</span>.addressinfo = addressinfo; } <span class="hljs-keyword">public</span> Set<User> <span class="hljs-title">getUser</span>() { <span class="hljs-keyword">return</span> user; } <span class="hljs-keyword">public</span> <span class="hljs-keyword">void</span> <span class="hljs-title">setUser</span>(Set<User> user) { <span class="hljs-keyword">this</span>.user = user; } }</code>
表结构:
user表
address表
user_address表
配置文件
User.hbm.xml:
<code class=" hljs applescript"><hibernate-mapping> <<span class="hljs-type">class</span> <span class="hljs-property">name</span>=<span class="hljs-string">"com.entity.User"</span> table=<span class="hljs-string">"user"</span>> <<span class="hljs-property">id</span> <span class="hljs-property">name</span>=<span class="hljs-string">"userid"</span> type=<span class="hljs-string">"java.lang.Integer"</span> column=<span class="hljs-string">"userid"</span>> <generator <span class="hljs-type">class</span>=<span class="hljs-string">"identity"</span>/> </<span class="hljs-property">id</span>> <<span class="hljs-keyword">property</span> <span class="hljs-property">name</span>=<span class="hljs-string">"name"</span> type=<span class="hljs-string">"java.lang.String"</span> column=<span class="hljs-string">"name"</span>> </<span class="hljs-keyword">property</span>> <<span class="hljs-keyword">property</span> <span class="hljs-property">name</span>=<span class="hljs-string">"password"</span> type=<span class="hljs-string">"java.lang.String"</span> column=<span class="hljs-string">"password"</span>> </<span class="hljs-keyword">property</span>> <<span class="hljs-keyword">set</span> <span class="hljs-property">name</span>=<span class="hljs-string">"address"</span> table=<span class="hljs-string">"user_address"</span> inverse=<span class="hljs-string">"true"</span>> <key> <column <span class="hljs-property">name</span>=<span class="hljs-string">"userid"</span>/> </key> <many-<span class="hljs-keyword">to</span>-many <span class="hljs-type">class</span>=<span class="hljs-string">"com.entity.Address"</span> column=<span class="hljs-string">"addressid"</span>/> </<span class="hljs-keyword">set</span>> </<span class="hljs-type">class</span>> </hibernate-mapping></code>
Address.hbm.xml
<code class=" hljs xml"><span class="hljs-tag"><<span class="hljs-title">hibernate-mapping</span>></span> <span class="hljs-tag"><<span class="hljs-title">class</span> <span class="hljs-attribute">name</span>=<span class="hljs-value">"com.entity.Address"</span> <span class="hljs-attribute">table</span>=<span class="hljs-value">"address"</span>></span> <span class="hljs-tag"><<span class="hljs-title">id</span> <span class="hljs-attribute">name</span>=<span class="hljs-value">"addressid"</span> <span class="hljs-attribute">type</span>=<span class="hljs-value">"java.lang.Integer"</span> <span class="hljs-attribute">column</span>=<span class="hljs-value">"addressid"</span>></span> <span class="hljs-tag"><<span class="hljs-title">generator</span> <span class="hljs-attribute">class</span>=<span class="hljs-value">"identity"</span>></span> <span class="hljs-tag"></<span class="hljs-title">generator</span>></span> <span class="hljs-tag"></<span class="hljs-title">id</span>></span> <span class="hljs-tag"><<span class="hljs-title">property</span> <span class="hljs-attribute">name</span>=<span class="hljs-value">"addressinfo"</span> <span class="hljs-attribute">type</span>=<span class="hljs-value">"java.lang.String"</span> <span class="hljs-attribute">column</span>=<span class="hljs-value">"addressinfo"</span>></span> <span class="hljs-tag"></<span class="hljs-title">property</span>></span> <span class="hljs-tag"><<span class="hljs-title">set</span> <span class="hljs-attribute">name</span>=<span class="hljs-value">"user"</span> <span class="hljs-attribute">table</span>=<span class="hljs-value">"user_address"</span>></span> <span class="hljs-tag"><<span class="hljs-title">key</span>></span> <span class="hljs-tag"><<span class="hljs-title">column</span> <span class="hljs-attribute">name</span>=<span class="hljs-value">"addressid"</span>/></span> <span class="hljs-tag"></<span class="hljs-title">key</span>></span> <span class="hljs-tag"><<span class="hljs-title">many-to-many</span> <span class="hljs-attribute">class</span>=<span class="hljs-value">"com.entity.User"</span> <span class="hljs-attribute">column</span>=<span class="hljs-value">"userid"</span>/></span> <span class="hljs-tag"></<span class="hljs-title">set</span>></span> <span class="hljs-tag"></<span class="hljs-title">class</span>></span> <span class="hljs-tag"></<span class="hljs-title">hibernate-mapping</span>></span></code>
测试类Test.java
<code class=" hljs avrasm">public class Test { public static void main(String[] args){ Session session = HibernateUtil<span class="hljs-preprocessor">.getSession</span>()<span class="hljs-comment">;</span> Transaction tx = session<span class="hljs-preprocessor">.beginTransaction</span>()<span class="hljs-comment">;</span> User u = new User()<span class="hljs-comment">;</span> u<span class="hljs-preprocessor">.setName</span>(<span class="hljs-string">"sbw"</span>)<span class="hljs-comment">;</span> u<span class="hljs-preprocessor">.setPassword</span>(<span class="hljs-string">"123"</span>)<span class="hljs-comment">; </span> User u1 = new User()<span class="hljs-comment">;</span> u1<span class="hljs-preprocessor">.setName</span>(<span class="hljs-string">"gaoya"</span>)<span class="hljs-comment">;</span> u1<span class="hljs-preprocessor">.setPassword</span>(<span class="hljs-string">"456"</span>)<span class="hljs-comment">;</span> Address a = new Address()<span class="hljs-comment">;</span> a<span class="hljs-preprocessor">.setAddressinfo</span>(<span class="hljs-string">"heu"</span>)<span class="hljs-comment">;</span> Address a1 = new Address()<span class="hljs-comment">;</span> a1<span class="hljs-preprocessor">.setAddressinfo</span>(<span class="hljs-string">"hrb"</span>)<span class="hljs-comment">;</span> a<span class="hljs-preprocessor">.getUser</span>()<span class="hljs-preprocessor">.add</span>(u)<span class="hljs-comment">;</span> a<span class="hljs-preprocessor">.getUser</span>()<span class="hljs-preprocessor">.add</span>(u1)<span class="hljs-comment">;</span> a1<span class="hljs-preprocessor">.getUser</span>()<span class="hljs-preprocessor">.add</span>(u)<span class="hljs-comment">;</span> a1<span class="hljs-preprocessor">.getUser</span>()<span class="hljs-preprocessor">.add</span>(u1)<span class="hljs-comment">;</span> u<span class="hljs-preprocessor">.getAddress</span>()<span class="hljs-preprocessor">.add</span>(a)<span class="hljs-comment">;</span> u<span class="hljs-preprocessor">.getAddress</span>()<span class="hljs-preprocessor">.add</span>(a1)<span class="hljs-comment">;</span> u1<span class="hljs-preprocessor">.getAddress</span>()<span class="hljs-preprocessor">.add</span>(a)<span class="hljs-comment">;</span> u1<span class="hljs-preprocessor">.getAddress</span>()<span class="hljs-preprocessor">.add</span>(a1)<span class="hljs-comment">;</span> session<span class="hljs-preprocessor">.save</span>(a)<span class="hljs-comment">;</span> session<span class="hljs-preprocessor">.save</span>(a1)<span class="hljs-comment">;</span> session<span class="hljs-preprocessor">.save</span>(u)<span class="hljs-comment">;</span> session<span class="hljs-preprocessor">.save</span>(u1)<span class="hljs-comment">;</span> tx<span class="hljs-preprocessor">.commit</span>()<span class="hljs-comment">;</span> HibernateUtil<span class="hljs-preprocessor">.closeSession</span>()<span class="hljs-comment">;</span> } }</code>
测试结果:

要优化MySQL慢查询,需使用slowquerylog和performance_schema:1.启用slowquerylog并设置阈值,记录慢查询;2.利用performance_schema分析查询执行细节,找出性能瓶颈并优化。

MySQL和SQL是开发者必备技能。1.MySQL是开源的关系型数据库管理系统,SQL是用于管理和操作数据库的标准语言。2.MySQL通过高效的数据存储和检索功能支持多种存储引擎,SQL通过简单语句完成复杂数据操作。3.使用示例包括基本查询和高级查询,如按条件过滤和排序。4.常见错误包括语法错误和性能问题,可通过检查SQL语句和使用EXPLAIN命令优化。5.性能优化技巧包括使用索引、避免全表扫描、优化JOIN操作和提升代码可读性。

MySQL异步主从复制通过binlog实现数据同步,提升读性能和高可用性。1)主服务器记录变更到binlog;2)从服务器通过I/O线程读取binlog;3)从服务器的SQL线程应用binlog同步数据。

MySQL是一个开源的关系型数据库管理系统。1)创建数据库和表:使用CREATEDATABASE和CREATETABLE命令。2)基本操作:INSERT、UPDATE、DELETE和SELECT。3)高级操作:JOIN、子查询和事务处理。4)调试技巧:检查语法、数据类型和权限。5)优化建议:使用索引、避免SELECT*和使用事务。

MySQL的安装和基本操作包括:1.下载并安装MySQL,设置根用户密码;2.使用SQL命令创建数据库和表,如CREATEDATABASE和CREATETABLE;3.执行CRUD操作,使用INSERT,SELECT,UPDATE,DELETE命令;4.创建索引和存储过程以优化性能和实现复杂逻辑。通过这些步骤,你可以从零开始构建和管理MySQL数据库。

InnoDBBufferPool通过将数据和索引页加载到内存中来提升MySQL数据库的性能。1)数据页加载到BufferPool中,减少磁盘I/O。2)脏页被标记并定期刷新到磁盘。3)LRU算法管理数据页淘汰。4)预读机制提前加载可能需要的数据页。

MySQL适合初学者使用,因为它安装简单、功能强大且易于管理数据。1.安装和配置简单,适用于多种操作系统。2.支持基本操作如创建数据库和表、插入、查询、更新和删除数据。3.提供高级功能如JOIN操作和子查询。4.可以通过索引、查询优化和分表分区来提升性能。5.支持备份、恢复和安全措施,确保数据的安全和一致性。

全表扫描在MySQL中可能比使用索引更快,具体情况包括:1)数据量较小时;2)查询返回大量数据时;3)索引列不具备高选择性时;4)复杂查询时。通过分析查询计划、优化索引、避免过度索引和定期维护表,可以在实际应用中做出最优选择。


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