我无法在jsp页面中呈现嵌套的父子树结构。由于stackover flow错误导致
<code><jsp:include page=""/></code>
我的数据库:
Id || Name || Parentid ||
1 || animal|| 0 ||
2 || Dog || 1 || etc.
模型类:
public class Node {
private int id;
private String name;
private int parentId;
private List<Node> children;
public Node() {
}
public Node(String name, int parentId, List<Node> children) {
this.name = name;
this.parentId = parentId;
this.children = children;
}
DAO 类:
@Override
public List<Node> nodelist() {
String sql = "select * from tree";
List<Node> listNode = jdbcTemplate.query(sql, new RowMapper<Node>() {
@Override
public Node mapRow(ResultSet rs, int rowNum) throws SQLException {
Node node = new Node();
node.setId(rs.getInt("id"));
node.setName(rs.getString("name"));
node.setParentId(rs.getInt("parent_id"));
return node;
}
});
return listNode;
}
在 Controller 中，我绑定(bind)对象如下:
List<Node> rootNodes;
@Autowired
TreeDao treeDao;
@RequestMapping(value = "/node", method = RequestMethod.GET)
public ModelAndView getallnodes(ModelAndView model) throws IOException {
//menuObj = menuDao.listCategory();
List<Node> listnode = treeDao.nodelist();
getInfiniteTree(listnode);
model.addObject("rootNodes",rootNodes);
model.setViewName("tree");
return model;
}
public List<Node> getInfiniteTree(List<Node> nodes) {
return findRootNodes(nodes);
}
private List<Node> findRootNodes(List<Node> nodes) {
rootNodes = new ArrayList<Node>();
for (Node node : nodes) {
if (node.getParentId() == 0) {
rootNodes.add(node);
findChildNodes(node, nodes);
}
}
System.out.println("rootnodes "+rootNodes);
Gson gson = new Gson();
System.out.println(gson.toJson(rootNodes));
//I got the correct json format data here.
//Collections.sort(rootNodes);
return rootNodes;
}
private void findChildNodes(Node parentNode, List<Node> nodes) {
List<Node> children = new ArrayList<Node>();
parentNode.setChildren(children);
for (Node node : nodes) {
if (node.getParentId() == parentNode.getId()) {
children.add(node);
findChildNodes(node, nodes);
}
}
//Collections.sort(children);
}
在另一个java swing项目中，我测试了类似的代码并得到了以下字符串结果:
nodes [Node{id=1, name=供应链部, parentId=0, sort=3, children=[Node{id=5, name=物流部, parentId=1, sort=1, children=[]}, Node{id=6, name=采购部, parentId=1, sort=2, children=[]}]}, Node{id=2, name=技术部, parentId=0, sort=1, children=[Node{id=7, name=开发部, parentId=2, sort=2, children=[Node{id=12, name=后端部, parentId=7, sort=2, children=[]}, Node{id=13, name=前端部, parentId=7, sort=2, children=[Node{id=14, name=diee, parentId=13, sort=2, children=[]}, Node{id=15, name=diee, parentId=13, sort=2, children=[]}]}]}, Node{id=8, name=测试部, parentId=2, sort=1, children=[]}, Node{id=9, name=运维部, parentId=2, sort=3, children=[]}]}, Node{id=3, name=行政部, parentId=0, sort=2, children=[Node{id=10, name=招聘部, parentId=3, sort=1, children=[]}, Node{id=11, name=人事部, parentId=3, sort=2, children=[]}]}, Node{id=4, name=公关部, parentId=0, sort=4, children=[]}]
问题是我无法使用jsp递归显示它，我尝试了下面的代码:
树.jsp:
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>JSP Page</title>
</head>
<body>
<c:set var="menuitem" value="${rootNodes}" scope="request" />
<jsp:include page="menuitem.jsp" />
</body>
</html>
menuitem.jsp:
<%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>
<ul>
<c:forEach var ="menuitems" items="${menuitem}">
<li><a href="#">${menuitems.name}</a></li>
<ul>
<c:if test="${fn:length(menuitems.children) gt 0}">
<li class="droprightMenu">
<c:out value="Has children"></c:out>
<c:forEach var="menuitemc" items="${menuitems.children}">
<c:set var="menuitem" value="${menuitemc}" scope="request" />
<%--<jsp:include page="menuitem.jsp" />--%>
</c:forEach>
</li>
</c:if>
</ul>
</c:forEach>
</ul>
它不包括通过无限子级的页面，并且由于我是 JSP 递归的新手，请忽略我的错误。我在这里呆了几天。 异常(exception):
Don't know how to iterate over supplied "items" in <forEach>
org.apache.jasper.JasperException: An exception occurred processing JSP page /WEB-INF/views/menuitem.jsp at line 14
11:
12:
13: <ul>
14: <c:forEach var ="menuitems" items="${menuitem}">
15: <li><a href="#">${menuitems.name}</a></li>
16: <ul>
17: <c:if test="${fn:length(menuitems.children) gt 0}">
最佳答案
menuitem.jsp
<c:forEach var="menuitem" items="${menuitem.children}">
<li><a href="#" id="${menuitem.id}"><i class="fa fa-circle-o"></i> <span>${menuitem.name} </span></a></li>
<c:set var="menuitem" value="${menuitem}" scope="request" />
<jsp:include page="/WEB-INF/views/menuitem.jsp" />
</c:forEach>
我认为问题就出在这里。尝试将 var="menuitem" 重命名为 var="childmenuitem。
我相信您当前不断将相同的对象传递到子菜单，从而导致无限循环。
关于java - 渲染父 subview 导致StackOverflow异常，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/46808718/