hibernate多表查询检索的几种方法。二

 

我做的两张表：一张department表，一张employee表，建表语句如下：

drop table employee

create table EMPLOYEE

(

ID      NUMBER(10) not null,

parentID   number(10),

NAME     VARCHAR2(20),

AGE      NUMBER(3),

PASSWARD VARCHAR2(12),

CSRQ     DATE,

PICTURE varchar(12),

primary key(id),

foreign key(parentID) references department(id)

)

drop table department

create table department

(

id number(10) not null,

dep_id varchar2(20),

dep_mc varchar2(20),

primary key(id)

)

其中，employee表中的parentID是department表的外键，department和employee表是一对多的关系，反过来是多对一的关系。怎么叫都可以。

Department.hbm.xml代码如下：

<hibernate-mapping>

    <class name="com.dudeng.employee.hibernate.vo.Department"

       table="DEPARTMENT" schema="DUDENG">

       <id name="id" type="java.lang.Long">

           <column name="ID" precision="10" scale="0" />

           <generator class="sequence">

              <param name="sequence">seq_department</param>

           </generator>

       </id>

       <property name="dep_id" type="java.lang.String">

           <column name="DEP_ID" length="20" not-null="false" />

       </property>

       <property name="dep_mc" type="java.lang.String">

           <column name="DEP_MC" length="20" not-null="false" />

       </property>

       <set name="employees" inverse="true">        

<key>

              <column name="parentID" precision="5" scale="0"

                  not-null="true" />

           </key>

           <one-to-many

              class="com.dudeng.employee.hibernate.vo.Employee" />

       </set>

    </class>

</hibernate-mapping>

Employee.hbm.xml的代码如下：

<hibernate-mapping>

    <class name="com.dudeng.employee.hibernate.vo.Employee"

       table="EMPLOYEE" schema="DUDENG">

       <id name="id" type="java.lang.Long">

           <column name="ID" precision="10" scale="0" />

           <generator class="sequence">

              <param name="sequence">seq_employee</param>

           </generator>

       </id>

<many-to-one name="department" class="com.dudeng.employee.hibernate.vo.Department">

                <column name="parentID" precision="5" scale="0" not-null="true" />

        </many-to-one>

       <property name="name" type="java.lang.String">

           <column name="NAME" length="20" not-null="false" />

        </property>

       <property name="age" type="java.lang.Long">

         <column name="AGE" precision="3" scale="0" not-null="false" />

       </property>

       <property name="passward" type="java.lang.String">

           <column name="PASSWARD" length="12" not-null="false" />

        </property>

       <property name="csrq" type="java.util.Date">

           <column name="CSRQ" length="7" not-null="false" />

       </property>

       <property name="picture" type="java.lang.String">

           <column name="PICTURE" length="20" not-null="false"/>

       </property>

    </class>

</hibernate-mapping>

查询结果集合：

List list = null;

String QueryStr = "from Employee emp,Department dep where emp.department = dep.id";

EmployeeBiz empbiz = EmployeeBiz.getInstance();

list = empbiz.find(QueryStr);

for (int i = 0; i < list.size(); i++)

{

    Object[] obj = (Object[]) list.get(i);

    for (int j = 0; j < obj.length; j++)

    {

       if (obj[j] instanceof Employee)

       {

           Employee emp = (Employee) obj[j];

           System.out.print(emp.getName());

       }

elseif (obj[j] instanceof Department)

       {

           Department dep = (Department) obj[j];

           System.out.print(dep.getDep_mc());

       }

    }

    System.out.println();

}

以上特别注意的地方：emp.department不能写成emp.parentID，我上网查了半天才找出原因的。开始写成emp.parentID了，后来改成emp.department程序运行正常了。

 

 

另外种方法
写个DocumentDetail对象，然后获得查询结果集合
select new com.cetc.bean.util.vo.DocumentDetail(da.contentid,dd.id,dd.filename,dd.filesource,dd.filesize,dd.mimetype,dd.author,dd.filepath) from DocumentDetail dd,ContentAttachment da where dd.id=da.documentid
构造函数一定要写好
public DocumentDetail(String contentid,String documentid,String fileName,String fileSource,Long fileSize,String mimeType,String author,String filePath){
   this.contentid = contentid;
   this.documentid = documentid;
   this.fileName = fileName;
   this.fileSource = fileSource;
   this.fileSize = fileSize;
   this.mimeType = mimeType;
   this.author = author;
   this.filePath = filePath;
}

 

最后 视图！！！ 哈哈哈