一百分解决一个HIBERNATE简单有关问题

一百分解决一个HIBERNATE简单问题
报错提示

Hibernate: select bulletin0_.id as x0_0_ from BULLETIN bulletin0_
java.lang.ClassCastException
at meis.tag.Bulletin_tag.doAfterBody(Bulletin_tag.java:48)
at jsp_servlet.__index._jspService(__index.java:202)
at weblogic.servlet.jsp.JspBase.service(JspBase.java:33)
at weblogic.servlet.internal.ServletStubImpl$ServletInvocationAction.run
(ServletStubImpl.java:1006)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubIm

代码

Query query=session.createQuery("select b.id from meis.hibernate.Bulletin as b");

java.util.List list=query.list();

result.append("<TABLE width=\"97%\" border=\"0\" cellspacing=\"6\" cellpadding=\"0\"><tr><td>dfdsfsdf"+list.size()+"</td></tr>");

Iterator iter = list.iterator();

while (iter.hasNext())
{
.....
}
/*
*/

映射类文件
package meis.hibernate;

public class Bulletin {

//发布日期

private String id;

private String issuedate;
private String title;

public String getId()
{
return id;
}
public void setId(String id)
{
this.id = id;
}

public String getIssuedate()
{
return issuedate;
}

public void setIssuedate(String issuedate)
{
this.issuedate = issuedate;
}

public String getTitle()
{
return title;
}
public void setTitle(String title)
{
this.title = title;
}

}

配置文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN" "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping>
<class name="meis.hibernate.Bulletin" table="BULLETIN">
<id name="id">
<generator class="assigned" />
</id>
<property name="issuedate" />
<property name="title" />
</class>

</hibernate-mapping>

[解决办法]
while (iter.hasNext())
{
.....
}
把其中的内容发上来
[解决办法]
用数组来解决吧

Object[] bulletin= (Object[]) iter.next();

bulletin[0]

bulletin[1]
[解决办法]
meis.hibernate.Bulletin bulletin=(meis.hibernate.Bulletin)iter.next();
转型错误
[解决办法]
Query query=session.createQuery("select b.id from meis.hibernate.Bulletin as b");
java.util.List list=query.list(); 中返回的不是Bulletin对象
好好对比一下!
[解决办法]
karlpan01 说到：
Query query=session.createQuery("select b.id from meis.hibernate.Bulletin as b");
java.util.List list=query.list(); 中返回的不是Bulletin对象
好好对比一下!

就是这个答案了。你的list里面现在放的是一些id,比如{1，2，3，4}，

而不是bulletin的对象{bulletin1,bulletin2,bulletin3,bulletin4}.

所以在结果list面的元素是不能用 getId()获是getTitle()这些方法的。

[解决办法]

Java code

Query query=session.createQuery("select b.id from meis.hibernate.Bulletin as b"); java.util.List list=query.list();
[解决办法]
若你想取部分字段的话，取出来的是List中每个单元里一个对象数组，每个数组其实就是一行记录。例如可以这样：

Java codeList ls = session.createQuery("select er.employerid,et.employmentid,et.startDate from Employer er left join er.employments as et")               .list();        for (Iterator itr = ls.iterator(); itr.hasNext(); )        {            Object[] oo = (Object[])itr.next();            for (int i = 0;i &lt; oo.length ;i++ )            {                System.out.println(oo[i]);            }            System.out.println("====================");        }
[解决办法]
貌似来晚了  
java.lang.ClassCastException 是 JVM 在检测到两个类型间的转换不兼容时引发的运行时异常

Query query=session.createQuery("select b.id from meis.hibernate.Bulletin as b");

[color=#FF0000]meis.hibernate.Bulletin bulletin=(meis.hibernate.Bulletin)iter.next();[/color]

类型不同啊~

一百分解决一个HIBERNATE简单有关问题

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