使用休眠查询多对多关系
[英]Query for Many-To-Many relation using hibernate
问题描述
我在使用休眠的资源类中具有多对多关系。 在类别类中：
@Entity
public class Category {
Id
@GeneratedValue
private long id;
@ManyToMany
@JoinTable(name = "category_activity",
joinColumns = { @JoinColumn(name = "Category_id") },
inverseJoinColumns = { @JoinColumn(name = "activities_id") })
private Collection<Activity> activities;
}
在Activity类中：
@Entity
public class Activity {
@Id
@GeneratedValue
private long id;
@ManyToMany
@JoinTable(name="category_activity",
joinColumns={@JoinColumn(name="activities_id")},
inverseJoinColumns={@JoinColumn(name="Category_id")})
private Collection<Category> category;
}
当我之间存在oneToMany关系时，我使用的查询对我来说很好：
Session session = HibernateUtil.getSessionFactory().getCurrentSession();
session.beginTransaction();
Collection<Activity> activities = (Collection<Activity>) session.createQuery("from Activity as a where a.category.id=" + categoryId + " order by a.key").list();
session.getTransaction().commit();
我很感谢我可以为ManyToMany关系解决此查询的任何帮助？
我也使用了这个查询：
activities = (List<Activity>) session.createQuery("from Activity a join a.category cs where cs.id= :categoryId order by a.key").setLong("categoryId", categoryId).list();
我在堆栈跟踪中得到此错误：
<html><head><title>Apache Tomcat/7.0.23 - Error report</title><style><!--H1 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:22px;} H2 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:16px;} H3 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:14px;} BODY {font-family:Tahoma,Arial,sans-serif;color:black;background-color:white;} B {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;} P {font-family:Tahoma,Arial,sans-serif;background:white;color:black;font-size:12px;}A {color : black;}A.name {color : black;}HR {color : #525D76;}--></style> </head><body><h1>HTTP Status 500 - </h1><HR size="1" noshade="noshade"><p><b>type</b> Exception report</p><p><b>message</b> <u></u></p><p><b>description</b> <u>The server encountered an internal error () that prevented it from fulfilling this request.</u></p><p><b>exception</b> <pre>java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to java.lang.Comparable
java.util.ComparableTimSort.countRunAndMakeAscending(Unknown Source)
java.util.ComparableTimSort.sort(Unknown Source)
java.util.ComparableTimSort.sort(Unknown Source)
java.util.Arrays.sort(Unknown Source)
java.util.Collections.sort(Unknown Source)
se.softwerk.timelog.controller.ActivityManager.activityList2(ActivityManager.java:64)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
java.lang.reflect.Method.invoke(Unknown Source)
com.sun.jersey.spi.container.JavaMethodInvokerFactory$1.invoke(JavaMethodInvokerFactory.java:60)
com.sun.jersey.server.impl.model.method.dispatch.AbstractResourceMethodDispatchProvider$ResponseOutInvoker._dispatch(AbstractResourceMethodDispatchProvider.java:205)
com.sun.jersey.server.impl.model.method.dispatch.ResourceJavaMethodDispatcher.dispatch(ResourceJavaMethodDispatcher.java:75)
com.sun.jersey.server.impl.uri.rules.HttpMethodRule.accept(HttpMethodRule.java:288)
com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
com.sun.jersey.server.impl.uri.rules.ResourceClassRule.accept(ResourceClassRule.java:108)
com.sun.jersey.server.impl.uri.rules.RightHandPathRule.accept(RightHandPathRule.java:147)
com.sun.jersey.server.impl.uri.rules.RootResourceClassesRule.accept(RootResourceClassesRule.java:84)
com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1469)
com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1400)
com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1349)
com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1339)
com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:416)
com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:537)
com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:708)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
</pre></p><p><b>note</b> <u>The full stack trace of the root cause is available in the Apache Tomcat/7.0.23 logs.</u></p><HR size="1" noshade="noshade"><h3>Apache Tomcat/7.0.23</h3></body></html>
1 个解决方案
解决方案1
1 已采纳 2012-07-07 03:58:01
首先，您不应该串联字符串，这为SQLInjection攻击打开了大门 ，您应该使用命名参数。 有关命名参数的更多信息，请点击此处
其次，如果您有ManyToMany关系，则双方应多元化：
这个
private Collection<Category> category;
应该是这样的：
private Collection<Category> categories;
现在关于您的特定问题，您有
from Activity as a where a.category.id= :categoryId order by a.key
你需要这个：
from Activity a join a.category cs where cs.id= :categoryId order by a.key
查询多对多关系中值的总和
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