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最近遇到了hibernate的一个问题

这几天一直没有更新我的博客是因为我遇到了一个棘手的问题,这是我编程以来困扰我时间最长的一个问题：从周一下午一直到现在。如果哪位高手有这方面的经验,请不吝指教:
这是个关于hibernate方面的问题:
我的数据库关联较多,hbm.xml是用myeclipse自动生成的.dao是spring的,也是myeclipse自动生成的.在用hibernate向数据库插入数据的时候,第一次执行还比较顺利,但把同样的数据再次插入的时候,代码就走不动了.(主键是自增长的,插入时不设值),但当我重启tomcat后,第一次执行插入又能插入了,但第二次执行的时候又走不动了...就这样周而复始.
我测试后发现经常被卡住的语句是类似下面的语句:
(某类)beanDAO.findByExample(某类实例).get(0);
请各位抽空看看.谢谢.
大家可以凭经验来判断一下这个问题.不用看代码.因为hbm.mxl 和dao都是myeclipse自动生成的,我没有改.
而程序中经常出错就这句.(某类)beanDAO.findByExample(某类实例).get(0);

现在我对这个问题总算有点思路了。但还没实现，请高手指教。

posted on 2006-08-17 14:07 智者无疆阅读(1416) 评论(8) 编辑收藏所属分类: about hibernate

评论:

# re: 最近遇到了hibernate的一个问题智者无疆 Posted @ 2006-08-17 14:10
注意出问题的这句是先从数据库里向外读一个数据，然后为插入其他表作准备。回复更多评论
# re: 最近遇到了hibernate的一个问题 Robin's Java World Posted @ 2006-08-17 21:57
你的DAO Bean是不是单例状态？如果是的话就改为非单态吧。回复更多评论
# re: 最近遇到了hibernate的一个问题 Red Posted @ 2006-08-17 23:25
由于 findByExample 操作，数据量过大有可能造成问题回复更多评论
# re: 最近遇到了hibernate的一个问题智者无疆 Posted @ 2006-08-18 09:17
谢谢robin 和red的提示，我会把试验结果放在这儿。回复更多评论
# re: 最近遇到了hibernate的一个问题智者无疆 Posted @ 2006-08-18 09:43
DAO改为非单态依然在第二次执行插入时不成功。依然是那个句子卡住了，下面我来想办法修理那个倒霉孩子.(某类)beanDAO.findByExample(某类实例).get(0); 回复更多评论
# re: 最近遇到了hibernate的一个问题 Binary Posted @ 2006-08-21 15:09
事务关闭了吗？回复更多评论
# re: 最近遇到了hibernate的一个问题智者无疆 Posted @ 2006-08-22 15:55
困扰了一个星期的错误，今天终于得以解决：
1，我的web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"">http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

<servlet>
<servlet-name>SpringContextServlet</servlet-name>
<servlet-class>org.springframework.web.context.ContextLoaderServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>

<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/applicationContext.xml</param-value>
</context-param>

<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>Fileupload</servlet-name>
<servlet-class>com.real.zlj.common.Fileupload</servlet-class>
</servlet>
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>DealExcel</servlet-name>
<servlet-class>com.real.zlj.common.DealExcel</servlet-class>
</servlet>
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>UploadExamPoins</servlet-name>
<servlet-class>com.real.zlj.common.UploadExamPoins</servlet-class>
</servlet>
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>DealExamPoins</servlet-name>
<servlet-class>com.real.zlj.common.DealExamPoins</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>Fileupload</servlet-name>
<url-pattern>/fileupload</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>DealExcel</servlet-name>
<url-pattern>/DealExcel</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>UploadExamPoins</servlet-name>
<url-pattern>/UploadExamPoins</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>DealExamPoins</servlet-name>
<url-pattern>/DealExamPoins</url-pattern>
</servlet-mapping>

</web-app>
2。applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">

<beans>

<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource">
<property name="driverClassName">
<value>com.microsoft.jdbc.sqlserver.SQLServerDriver</value>
</property>
<property name="url">
<value>jdbc:microsoft:sqlserver://localhost:1433</value>
</property>
<property name="username">
<value>sa</value>
</property>
</bean>
<bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
<property name="dataSource">
<ref bean="dataSource" />
</property>
<property name="hibernateProperties">
<props>
<prop key="hibernate.dialect">org.hibernate.dialect.SQLServerDialect</prop>
<prop key="hibernate.show_sql">true</prop>
</props>
</property>

<property name="mappingResources">
<list>
<value>com/real/zlj/hibernate/classes/UserInfo.hbm.xml</value>
<value>com/real/zlj/hibernate/classes/StAttendance.hbm.xml</value>
<value>com/real/zlj/hibernate/classes/FaAttendance.hbm.xml</value>
<value>com/real/zlj/hibernate/classes/ExClass.hbm.xml</value>
<value>com/real/zlj/hibernate/classes/Syllabus.hbm.xml</value>
<value>com/real/zlj/hibernate/classes/Result.hbm.xml</value>
<value>com/real/zlj/hibernate/classes/Faculty.hbm.xml</value>
<value>com/real/zlj/hibernate/classes/Subject.hbm.xml</value>
<value>com/real/zlj/hibernate/classes/ScGlory.hbm.xml</value>
<value>com/real/zlj/hibernate/classes/ScTeacher.hbm.xml</value>
<value>com/real/zlj/hibernate/classes/ScBulletin.hbm.xml</value>
<value>com/real/zlj/hibernate/classes/ClassInfo.hbm.xml</value>
<value>com/real/zlj/hibernate/classes/Department.hbm.xml</value>
<value>com/real/zlj/hibernate/classes/Exam.hbm.xml</value>
<value>com/real/zlj/hibernate/classes/School.hbm.xml</value>
<value>com/real/zlj/hibernate/classes/Students.hbm.xml</value>
</list>
</property>
</bean>


<bean id="myTransactionManager"
class="org.springframework.orm.hibernate3.HibernateTransactionManager">
<property name="sessionFactory">
<ref bean="sessionFactory"/>
</property>
</bean>

<bean id="FacultyTarget" class="com.real.zlj.services.FacultyImp">
<property name="facultyDao">
<ref bean="FacultyDAO"/>
</property>
</bean>

<bean id="ExClassTarget" class="com.real.zlj.services.ExClassImp">
<property name="exClassDAO">
<ref bean="ExClassDAO"/>
</property>
</bean>
<bean id="ClassInfoTarget" class="com.real.zlj.services.ClassInfoImp">
<property name="classDao">
<ref bean="ClassInfoDAO"/>
</property>
</bean>
<bean id="SchoolTarget" class="com.real.zlj.services.SchoolImp">
<property name="schoolDao">
<ref bean="SchoolDAO"/>
</property>
</bean>
<bean id="StudentsTarget" class="com.real.zlj.services.StudentImp">
<property name="studentDAO">
<ref bean="StudentsDAO"/>
</property>
</bean>
<bean id="ExamTarget" class="com.real.zlj.services.ExamImp">

<property name="examDAO">
<ref bean="ExamDAO"/>
</property>
</bean>
<bean id="DepartTarget" class="com.real.zlj.services.DepartImp">
<property name="departDAO">
<ref local="DepartmentDAO"/>
</property>
</bean>



<bean id="FacultyService" class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">
<property name="proxyInterfaces">
<list>
<value>com.real.zlj.services.IFaculty</value>
</list>
</property>
<property name="target">
<ref local="FacultyTarget"/>
</property>
<property name="transactionManager">
<ref local="myTransactionManager"/>
</property>
<property name="transactionAttributes">
<props >
<prop key="get*">PROPAGATION_REQUIRED,readOnly</prop>
<prop key="save*">PROPAGATION_REQUIRED</prop>
</props>
</property>
</bean>

<bean id="ExClassService" class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">
<property name="target">
<ref local="ExClassTarget"/>
</property>
<property name="transactionManager">
<ref local="myTransactionManager"/>
</property>
<property name="transactionAttributes">
<props>
<prop key="get*">PROPAGATION_REQUIRED,readOnly</prop>
<prop key="save*">PROPAGATION_REQUIRED</prop>
</props>
</property>
</bean>

<bean id="ClassInfoService" class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">
<property name="target">
<ref local="ClassInfoTarget"/>
</property>
<property name="transactionManager">
<ref local="myTransactionManager"/>
</property>
<property name="transactionAttributes">
<props>
<prop key="get*">PROPAGATION_REQUIRED,readOnly</prop>
<prop key="save*">PROPAGATION_REQUIRED</prop>
</props>
</property>
</bean>

<bean id="SchoolService" class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">
<property name="target">
<ref local="SchoolTarget"/>
</property>
<property name="transactionManager">
<ref local="myTransactionManager"/>
</property>
<property name="transactionAttributes">
<props>
<prop key="get*">PROPAGATION_REQUIRED,readOnly</prop>
<prop key="save*">PROPAGATION_REQUIRED</prop>
</props>
</property>
</bean>

<bean id="StudentsService" class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">
<property name="target">
<ref local="StudentsTarget"/>
</property>
<property name="transactionManager">
<ref local="myTransactionManager"/>
</property>
<property name="transactionAttributes">
<props>
<prop key="get*">PROPAGATION_REQUIRED,readOnly</prop>
<prop key="save*">PROPAGATION_REQUIRED</prop>
</props>
</property>
</bean>
<bean id="ExamService" class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">
<property name="target">
<ref local="ExamTarget"/>
</property>
<property name="transactionManager">
<ref local="myTransactionManager"/>
</property>
<property name="transactionAttributes">
<props>
<prop key="get*">PROPAGATION_REQUIRED,readOnly</prop>
<prop key="save*">PROPAGATION_REQUIRED</prop>
</props>
</property>
</bean>

<bean id="DepartService" class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean">
<property name="target">
<ref local="DepartTarget"/>
</property>
<property name="transactionManager">
<ref local="myTransactionManager"/>
</property>
<property name="transactionAttributes">
<props>
<prop key="get*">PROPAGATION_REQUIRED,readOnly</prop>
<prop key="save*">PROPAGATION_REQUIRED</prop>
</props>
</property>
</bean>

<bean id="UserInfoDAO" class="com.real.zlj.hibernate.classes.UserInfoDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>
<bean id="StAttendanceDAO" class="com.real.zlj.hibernate.classes.StAttendanceDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>
<bean id="FaAttendanceDAO" class="com.real.zlj.hibernate.classes.FaAttendanceDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>
<bean id="ExClassDAO" class="com.real.zlj.hibernate.classes.ExClassDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>
<bean id="SyllabusDAO" class="com.real.zlj.hibernate.classes.SyllabusDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>
<bean id="ResultDAO" class="com.real.zlj.hibernate.classes.ResultDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>
<bean id="FacultyDAO" class="com.real.zlj.hibernate.classes.FacultyDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>
<bean id="SubjectDAO" class="com.real.zlj.hibernate.classes.SubjectDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>
<bean id="ScGloryDAO" class="com.real.zlj.hibernate.classes.ScGloryDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>
<bean id="ScTeacherDAO" class="com.real.zlj.hibernate.classes.ScTeacherDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>
<bean id="ScBulletinDAO" class="com.real.zlj.hibernate.classes.ScBulletinDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>
<bean id="ClassInfoDAO" class="com.real.zlj.hibernate.classes.ClassInfoDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>
<bean id="DepartmentDAO" class="com.real.zlj.hibernate.classes.DepartmentDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>
<bean id="ExamDAO" class="com.real.zlj.hibernate.classes.ExamDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>
<bean id="SchoolDAO" class="com.real.zlj.hibernate.classes.SchoolDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>
<bean id="StudentsDAO" class="com.real.zlj.hibernate.classes.StudentsDAO">
<property name="sessionFactory">
<ref bean="sessionFactory" />
</property>
</bean>

</beans>

3.写service层的接口

4。写service层的实现类。

注意（1）一定要继承它的接口。

（2）写setXxDao()时，XxDao一定要和他的属性xxDao相对应。

（3）findByExample(某类实例）特别好用，但findByName()经常查询失败。

（4）别忘了老朋友：ServletContext sc = request.getSession().getServletContext();
WebApplicationContext wac = WebApplicationContextUtils
.getRequiredWebApplicationContext(sc);

（5）poi的关键的几句：

FileInputStream fis = new FileInputStream(fNew);
POIFSFileSystem fs = new POIFSFileSystem(fis);
HSSFWorkbook workbook = new HSSFWorkbook(fs);
// 创建一个文件后，开始各个表单的循环
int sheetNum = 2;
out.print("此excel工作薄表单数为:"
+ workbook.getNumberOfSheets());
out.print("<br/>");
for (sheetNum = 1; sheetNum <= workbook.getNumberOfSheets(); sheetNum++) {
HSSFSheet sheet = workbook.getSheet("Sheet" + sheetNum);
out.println("<font color='red' >表单" + sheetNum+ " 开始处理...</font><br>");
// 创建一个表单后，开始每行的循环*** 此处还要检查getLastRowNum()得到的意思
for (int i = sheet.getFirstRowNum()+1; i <= sheet.getLastRowNum(); i++) {
HSSFRow row = sheet.getRow(i);

typeid = row.getCell((short) 0).getCellType();

回复更多评论
# re: 最近遇到了hibernate的一个问题 xiaobai Posted @ 2006-08-31 15:52
spring生成的dao的方法有时候不好用
例如：用getById(id)不好用的时候，可以用getByExample试试。回复更多评论

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