一、左侧树形菜单数据分析

二、获取数据库表中的所有菜单数据

三、将菜单表中的数据在后台构建父子关系

四、前端代码实现

上期回顾，我们已经把登录界面完成并实现了功能，登录成功后能跳转到main.jsp页面，今天所要实现的一个功能就是main.jsp界面（主界面）左侧的树形菜单能够从数据库动态加载出来。

一、左侧树形菜单数据分析
今天所涉及的一个权限表如下：

接下来可以打开LayUi的官网：在线示例 - Layui

在里面去根据预览效果找关于菜单的源代码：

要么在文档中：

要么在示例中：

两者皆可~

将相关代码复制到我们的主界面（main.jsp）内，然后根据我们的数据库表对字面做出一些更改，运行效果如下：

然后我们通过图来进行分析这个树形菜单：

[

        {name:会议管理,children:[

{name:发布会议}，

        {name:我的会议}，

        {name:会议通知}，

        {name:历史会议}

        ] },

        {name:menu group2},

        {name:click menu item},

        {name:the links}

]

以上就是我们的数据结构分析。

二、获取数据库表中的所有菜单数据新建一个Permission实体类：

package com.zking.entity;

public class Permission {
	private long id;
	private String name;//菜单名
	private String description;//描述
	private String url;//点击菜单跳转页面
	private long pid;//父级菜单的ID
	private int ismenu;// 菜单/按钮
	private int displayno;//显示的顺序
	public Permission() {
		// TODO Auto-generated constructor stub
	}
	public long getId() {
		return id;
	}
	public void setId(long id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getDescription() {
		return description;
	}
	public void setDescription(String description) {
		this.description = description;
	}
	public String getUrl() {
		return url;
	}
	public void setUrl(String url) {
		this.url = url;
	}
	public long getPid() {
		return pid;
	}
	public void setPid(long pid) {
		this.pid = pid;
	}
	public int getIsmenu() {
		return ismenu;
	}
	public void setIsmenu(int ismenu) {
		this.ismenu = ismenu;
	}
	public int getDisplayno() {
		return displayno;
	}
	public void setDisplayno(int displayno) {
		this.displayno = displayno;
	}
	public Permission(long id, String name, String description, String url, long pid, int ismenu, int displayno) {
		super();
		this.id = id;
		this.name = name;
		this.description = description;
		this.url = url;
		this.pid = pid;
		this.ismenu = ismenu;
		this.displayno = displayno;
	}
	@Override
	public String toString() {
		return "Permission [id=" + id + ", name=" + name + ", description=" + description + ", url=" + url + ", pid="
				+ pid + ", ismenu=" + ismenu + ", displayno=" + displayno + "]";
	}
	
}

新建一个PermissionDao:

package com.zking.dao;

import java.util.List;

import com.zking.entity.Permission;
import com.zking.util.BaseDao;
import com.zking.util.PageBean;

public class PermissionDao  extends BaseDao{
//	查询t_oa_permission表中的数据
	public List list(Permission permission, PageBean pageBean) throws Exception {
		String sql="select * from t_oa_permission";
		return super.executeQuery(sql, Permission.class, pageBean);
	}
}

接着用juint4测试：

package com.zking.dao;

import static org.junit.Assert.*;

import java.util.List;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.zking.entity.Permission;

public class PermissionDaoTest {
	private PermissionDao pd=new PermissionDao();
	@Before
	public void setUp() throws Exception {
	}

	@After
	public void tearDown() throws Exception {
	}

	@Test
	public void testList() {
		try {
			List list = pd.list(null, null);
			for (Permission permission : list) {
				System.out.println(permission);
			}
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

}

运行结果显示已经获取数据库表中的所有菜单数据~

三、将菜单表中的数据在后台构建父子关系

BuildTree:

package com.zking.util;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class BuildTree {

	
	public static  TreeVo build(List> nodes) {

		if (nodes == null) {
			return null;
		}
		List> topNodes = new ArrayList>();

		for (TreeVo children : nodes) {
			String pid = children.getParentId();
			if (pid == null || "-1".equals(pid)) {
				topNodes.add(children);

				continue;
			}

			for (TreeVo parent : nodes) {
				String id = parent.getId();
				if (id != null && id.equals(pid)) {
					parent.getChildren().add(children);
					children.setHasParent(true);
					parent.setChildren(true);
					continue;
				}
			}

		}

		TreeVo root = new TreeVo();
		if (topNodes.size() == 1) {
			root = topNodes.get(0);
		} else {
			root.setId("000");
			root.setParentId("-1");
			root.setHasParent(false);
			root.setChildren(true);
			root.setChecked(true);
			root.setChildren(topNodes);
			root.setText("顶级节点");
			Map state = new HashMap<>(16);
			state.put("opened", true);
			root.setState(state);
		}

		return root;
	}

	
	public static  List> buildList(List> nodes, String idParam) {
		if (nodes == null) {
			return null;
		}
		List> topNodes = new ArrayList>();

		for (TreeVo children : nodes) {

			String pid = children.getParentId();
			if (pid == null || idParam.equals(pid)) {
				topNodes.add(children);

				continue;
			}

			for (TreeVo parent : nodes) {
				String id = parent.getId();
				if (id != null && id.equals(pid)) {
					parent.getChildren().add(children);
					children.setHasParent(true);
					parent.setChildren(true);

					continue;
				}
			}

		}
		return topNodes;
	}

}

TreeVo:

package com.zking.util;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;


public class TreeVo {
	
	private String id;
	
	private String text;
	
	private Map state;
	
	private boolean checked = false;
	
	private Map attributes;

	
	private List> children = new ArrayList>();

	
	private String parentId;
	
	private boolean hasParent = false;
	
	private boolean hasChildren = false;

	public String getId() {
		return id;
	}

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

	public String getText() {
		return text;
	}

	public void setText(String text) {
		this.text = text;
	}

	public Map getState() {
		return state;
	}

	public void setState(Map state) {
		this.state = state;
	}

	public boolean isChecked() {
		return checked;
	}

	public void setChecked(boolean checked) {
		this.checked = checked;
	}

	public Map getAttributes() {
		return attributes;
	}

	public void setAttributes(Map attributes) {
		this.attributes = attributes;
	}

	public List> getChildren() {
		return children;
	}

	public void setChildren(List> children) {
		this.children = children;
	}

	public boolean isHasParent() {
		return hasParent;
	}

	public void setHasParent(boolean isParent) {
		this.hasParent = isParent;
	}

	public boolean isHasChildren() {
		return hasChildren;
	}

	public void setChildren(boolean isChildren) {
		this.hasChildren = isChildren;
	}

	public String getParentId() {
		return parentId;
	}

	public void setParentId(String parentId) {
		this.parentId = parentId;
	}

	public TreeVo(String id, String text, Map state, boolean checked, Map attributes,
                  List> children, boolean isParent, boolean isChildren, String parentID) {
		super();
		this.id = id;
		this.text = text;
		this.state = state;
		this.checked = checked;
		this.attributes = attributes;
		this.children = children;
		this.hasParent = isParent;
		this.hasChildren = isChildren;
		this.parentId = parentID;
	}

	public TreeVo() {
		super();
	}

}

PermissionDao:

package com.zking.dao;

import java.util.ArrayList;
import java.util.List;

import com.zking.entity.Permission;
import com.zking.util.BaseDao;
import com.zking.util.BuildTree;
import com.zking.util.PageBean;
import com.zking.util.TreeVo;

public class PermissionDao  extends BaseDao{
//	查询t_oa_permission表中的数据
	public List list(Permission permission, PageBean pageBean) throws Exception {
		String sql="select * from t_oa_permission";
		return super.executeQuery(sql, Permission.class, pageBean);
	}
	
	public List> menus(Permission permission, PageBean pageBean) throws Exception {
		List> trees=new ArrayList>();
//		从数据路中拿到的菜单数据，此时数据是平级的，不具备父子关系
		List list = this.list(permission, pageBean);
		for (Permission p : list) {
			TreeVo vo = new TreeVo<>();
			vo.setId(p.getId()+"");
			vo.setText(p.getName());//节点的名称
			vo.setParentId(p.getPid()+"");
			trees.add(vo);
		}
		return BuildTree.buildList(trees, "-1");
	}
}

四、前端代码实现新建一个 PermissionAction：

package com.zking.web;

import java.util.List;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.zking.dao.PermissionDao;
import com.zking.entity.Permission;
import com.zking.framework.ActionSupport;
import com.zking.framework.ModelDriver;
import com.zking.util.ResponseUtil;
import com.zking.util.TreeVo;

public class PermissionAction extends ActionSupport implements ModelDriver{
	private Permission Permission=new Permission();
	PermissionDao pd=new PermissionDao();
	@Override
	public Permission getModel() {
		// TODO Auto-generated method stub
		return null;
	}

	public String menus(HttpServletRequest req, HttpServletResponse resp) {
		try {
			List> menus = pd.menus(null, null);
			//向前端响应树形结构的数据
			ResponseUtil.writeJson(resp, menus);
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return null;
	}
}

main.jsp :

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ include file="common/header.jsp" %>




Insert title here



  
    layout demo
    
    
      
      
        
      
      
      nav 1
      nav 2
      nav 3
      
        nav groups
        
          menu 11
          menu 22
          menu 33
        
      
    
    
    
      
        
          
         	 杨总
        
        
          Your Profile
          Settings
          Sign out
        
      
      
        
          
        
      
    
  
  
  
    
      
      
        
          会议管理1
          
            发布会议
            我的会议
            会议通知
            历史会议
          
        
        
          menu group 2
          
            list 1
            list 2
            超链接
          
        
        click menu item
        the links 
      
    
  
  
  
    
    内容主体区域。记得修改 layui.css 和 js 的路径
  
  
  
    
            底部固定区域

效果如下：

LayUI之动态树

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