报错是"Missing classpath entry C:/jboss-5.0.0.GA/server/default/lib/mail.jar"

这个问题在eclipse的bug中心可以找到 https://bugs.eclipse.org/bugs/show_bug.cgi?id=257823

原因是JBoss 5.0 GA release的目录结构和之前不一样了，而eclipse的对应插件没有相应的更改

解决办法：

到下面的目录中修改jboss5.serverdef

C:\ejb3\eclipse-jee-ganymede-SR1-win32\plugins\org.eclipse.jst.server.generic.jboss_1.5.205.v200805140145\servers\jboss5.serverdef

找到下面这一段并且做相应的修改

Xml代码

1. <classpath id="jboss.project" >
4. <fileset dir="${serverRootDirectory}">
5. <include name="client/*.jar" />
6. <include name="server/default/lib/*.jar" />
8. <include name="server/default/deployers/jbossweb.deployer/jsf-libs/*.jar" />
10. <!-- This will be ignored if EJB3 is not there 5.0 -->
11. <include name="lib/*.jar" />
12. <include name="server/default/deployers/jbossweb.deployer/*.jar" />
13. <include name="server/default/deployers/jboss-aop-jboss5.deployer/*.jar" />
14. <include name="server/default/deployers/ejb3.deployer/jboss-annotations-ejb3.jar" />
16. <!-- for validation to work this library is defined as an archive -->
17. <exclude name="common/lib/mail.jar" />
18. </fileset>
20. <!-- leave one generic jar as an archive so that validation works -->
21. <archive path="${serverRootDirectory}/common/lib/mail.jar" />
23. </classpath>

1.直接在类中赋值(推荐这种方式，因为这种方式可以使业务逻辑集中，并实现比较复杂的业务逻辑)

class Test {

    private Long count = 3L;

    @Column(name = "count", nullable = false)
    public Long getCount() {
        return count;
    }

}

2.通过columnDefinition来声明缺省值。

class Test {

	private Long count = 3L;

	@Column(name = "count", nullable = false, columnDefinition = "bigint(20) default 0")
	public Long getCount() {
		return count;
	}

}

注意：这时数据库类型一定要自己指定，Hibernate不会再为你指定数据库列的类型。如果没指定，在hbm2dll时就会抛出异常。

如果object是瞬时的(transient),就会抛出异常(org.hibernate.TransientObjectException)。

原因是:cascade="all"没设置。