dtree 通过从数据库的信息添加到节点信息中遇到的问题
前面已经做好，可以通过添加节点信息到数据库，然后在运动dtree的时候，碰到很多问题，先看代码

public List<tree> allTree() throws Exception{

		List<tree> list = getTreeService().listTree();

		return list;

	}

想通过这段代码获得数据库中节点信息的一个集合

<div class="dtree">

			<script type="text/javascript">

    		tree=new dTree("tree");

    		<%response.setCharacterEncoding("UTF-8");

    		list_tree lt = new list_tree();

    		Iterator<tree> dtolte = lt.allTree().iterator();

    		while(dtolte.hasNext()){

    			tree tr = dtolte.next();

    		%>	

    		tree.add('<%=tr.getNodeId()%>','<%=tr.getPreId()%>','forward.jsp?name=<%=tr.getName()%>');

    		<%

    		}

    		%>

    		document.write(tree);

    	</script>

		</div>

想通过这段代码来向节点中添加信息（仿照静态节点直接添加信息的过程加了个循环）

然后就出现这样的问题

org.apache.jasper.JasperException: java.lang.NullPointerException

	org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:522)

	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:416)

	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)

	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)

	javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

	org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:389)





root cause 



java.lang.NullPointerException

	com.tree.save.action.list_tree.allTree(list_tree.java:88)

	org.apache.jsp.tree2_jsp._jspService(tree2_jsp.java:84)

	org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)

	javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)

	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)

	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)

	javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

	org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:389)

还请看看是哪里出的问题