我使用Hibernate,我有这个查询：
List<Person> list = sess.createQuery("from Person").list();
有了这个声明,我得到所有的人从数据库.
但现在我只想要一些人.
我的数据库方案：
项目< - Project_Person - >人
所以我只想要一个项目的成员.
select * from Person inner join Project_Person
on person_id = id
where project_id = 1;
所以我想,我可以用Hibernate写这个：
List<Person> list =
sess.createQuery(
"from Person inner join Project_Person
on person_id = id
where project_id = "+projectId).list();
但是在这里我得到一个错误：
SERVE: Servlet.service() for servlet myproject3 threw exception org.hibernate.hql.ast.QuerySyntaxException: unexpected token: on near line 1,column 65 [from com.mydomain.myproject.domain.Person inner join Project_Person on person_id = id where project_id = 1] at org.hibernate.hql.ast.QuerySyntaxException.convert(QuerySyntaxException.java:54) at org.hibernate.hql.ast.QuerySyntaxException.convert(QuerySyntaxException.java:47) at org.hibernate.hql.ast.ErrorCounter.throwQueryException(ErrorCounter.java:82) at org.hibernate.hql.ast.QueryTranslatorImpl.parse(QueryTranslatorImpl.java:284) at org.hibernate.hql.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:182) at org.hibernate.hql.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:136) at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:101) at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:80) at org.hibernate.engine.query.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:124) at org.hibernate.impl.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:156) at org.hibernate.impl.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:135) at org.hibernate.impl.SessionImpl.createQuery(SessionImpl.java:1770) at sun.reflect.GeneratedMethodAccessor33.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:344) at $Proxy26.createQuery(Unknown Source) ...
有人有什么想法吗？
最好的祝福.
新错误：
SERVE: Servlet.service() for servlet myproject3 threw exception org.hibernate.QueryException: could not resolve property: project of: com.mydomain.myproject.domain.Person [from com.mydomain.myproject.domain.Person p where p.project.id = :id]
n：m关系：
@ManyToMany(cascade = CascadeType.ALL)
@JoinTable(name = "Project_Person",joinColumns = {@JoinColumn(name="project_id",referencedColumnName="id")},inverseJoinColumns = {@JoinColumn(name="person_id",referencedColumnName="id")}
)
private Set<Person> persons = new HashSet<Person>();
@ManyToMany(mappedBy="persons")
private Set<Project> projects = new HashSet<Project>();
全错误
Hibernate: select project0_.id as id1_,project0_.createDate as create2_1_,project0_.description as descript3_1_,project0_.name as name1_ from Project project0_ where project0_.id=1 Hibernate: select person0_.id as id0_0_,project2_.id as id1_1_,person0_.email as email0_0_,person0_.firstName as firstName0_0_,person0_.lastName as lastName0_0_,project2_.createDate as create2_1_1_,project2_.description as descript3_1_1_,project2_.name as name1_1_ from Person person0_ inner join Project_Person projects1_ on person0_.id=projects1_.person_id inner join Project project2_ on projects1_.project_id=project2_.id where project2_.id=? 15.12.2010 16:42:26 org.apache.catalina.core.ApplicationDispatcher invoke SERVE: Servlet.service() for servlet myproject3 threw exception java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to com.mydomain.myproject.domain.Person
解决方法
HQL查询是针对对象模型编写的,而不是针对数据库模式.
因此,您的查询取决于如何映射人员和项目之间的关系.例如,在Person中通过项目属性与Project具有多对一关系,查询将如下所示：
List<Person> list = sess.createQuery(
"from Person p where p.project.id = :id")
.setParameter("id",projectId)
.list();
编辑：在您需要多对多关系的情况下
select p from Person p join p.projects proj where proj.id = :id
也不是通过字符串连接传递参数是不好的做法,而是使用setParameter().
