如何使用hibernate查询连接表？ [英] how to query the join table using hibernate?

问题描述

我在Oracle SQL Developer中创建了三个表，即
$ b

1.Test_Employee2

2.Test_Project2

3.Employee_Project2 。

表格 Employee_Project2 是连接表，作为 Test_Project2 和 Employee_Project2 是多对多。

在hibernate中，我创建了两个hibernate类 TestEmployee 和 TestProject 分别为 Test_Project2 和 Employee_Project2 表格>
，表 Employee_Project2 定义在 TestProject hibernate类中，如下所示：

  @ManyToMany（cascade = CascadeType.ALL）
 @JoinTable（name =Employee_Project2，joinColumns = @JoinColumn（name =proj_id ），inverseJoinColumns = @JoinColumn（name =emp_id））
 private Set< TestEmployee> employeesList; 
  

我填充了表 Test_Project2 和 Employee_Project2 和一些记录，并且连接表 Employee_Project2 自动填充了一些记录。
现在我现在面临的问题是，我想在连接表 Employee_Project2 上使用hiberante的简单select语句，如下所示：

  String hql =FROM Employee_Project2; 
 Query query = session.createQuery（hql）; 
列表结果= query.list（）; 
 
 for（Object row：results）{
 //在这里做什么
} 
  

尽管连接表'Employee_Project2'不是一个hibernate类，我该如何做到这一点？



update strong>：



我想检索hibernate表TestProject中的所有记录，所以我写了下面的代码：



  String hql =FROM TestProject; 
 Query query = session.createQuery（hql）; 
列表结果= query.list（）; 
 System.out.println（results.get（0）+ results.get（0）.toString（））; 
  

现在的问题是，在运行时我收到类似以下的内容：



  results.get（0）msc.hibernate.persistence.TestProject@12ec9534 
  

如何获取每行中包含的值？


解决方案

你想要做的是创建类型化查询。通过适当的映射，您可以获得相关对象 - 无需查询连接表为 ORM 将为您执行此操作：

 查询查询= session.createQuery（hql）; 
 List< TestProject> results = query.list（）; 
 
（TestProject row：results）{
 //在这里做什么
 //做任何你想做的事
} 
  

使用propper关系映射，您可以获得像这样的关系：



 （TestProject row：results）{
 Set< TestEmployee>员工= row.getEmployeesList（）; 
 //做更多工作。 
} 
  

至于如何 - 主题过于宽泛无法覆盖在单个答案等，但你应该能够从这里开始 - http://hibernate.org/orm /documentation/5.1/

I have created three tables in Oracle SQL Developer namely

1.Test_Employee2
2.Test_Project2
3.Employee_Project2.
The table Employee_Project2 is the join table as the relation between Test_Project2 and Employee_Project2 is Many-To-Many.
In hibernate I created to two hibernate classes TestEmployee and TestProject for Test_Project2 and Employee_Project2 tables respectively,
and the table Employee_Project2 was defined in TestProject hibernate class as follows:

@ManyToMany(cascade = CascadeType.ALL)
@JoinTable(name = "Employee_Project2", joinColumns = @JoinColumn(name = "proj_id"), inverseJoinColumns = @JoinColumn(name = "emp_id"))
private Set<TestEmployee> employeesList;

I populated the tables Test_Project2 and Employee_Project2 with some records, and the join table Employee_Project2 automatically got populated with some records. now the problem I am facing currently is, I want to use a simple select statement on the join table Employee_Project2 using hiberante as follows:

String hql = "FROM Employee_Project2";
    Query query = session.createQuery(hql);
    List results = query.list();

    for (Object row : results) {
        //what to do here
    }

how can I do that despite the join table 'Employee_Project2' is not a hibernate class.?

update:

I would like to retrieve all the records in the hibernate table "TestProject", so i wrote the following code

String hql = "FROM TestProject";
Query query = session.createQuery(hql);
List results = query.list();
System.out.println("results.get(0)" + results.get(0).toString());

now the problem is, at run time i receive something like the following

results.get(0)msc.hibernate.persistence.TestProject@12ec9534

how can i get the values contained in the each row??

解决方案

What you want to do is to create typed query. With proper mapping you can get related objects as well - no need to query join tables as ORM will do this for you:

Query query = session.createQuery(hql);
List<TestProject> results = query.list();

for (TestProject row : results) {
    //what to do here
    // do whatever you want
}

And with propper relation mapping you can get relations like this:

for (TestProject row : results) {
    Set<TestEmployee> employees=row.getEmployeesList();
    // do more work.
}

As for "how to"s - the topic is too broad to cover it in single answer etc. but you should be able to start from here - http://hibernate.org/orm/documentation/5.1/

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