一、数据分析

我们来看一下今天案例的菜单数据库

根据数据库的数据

一级菜单为：书籍管理、订单管理（商家）、订单管理（会员）

所属书籍管理的二级菜单为：新增、未上架、已上架、已下架

所属订单管理（商家）的二级菜单为：未发货、已发货、已签收

所属订单管理（会员）的二级菜单为：未发货、已发货、已签收、订单项

二、获取数据库中数据

实体类Permission：

package com.zking.entity;

//数据库中t_oa_Permission表对应的实体类
public class Permission {
	private long id;//id
	private String name;//菜单名
	private String description;//菜单描述
	private String url;//点击菜单跳转页面
	private long pid;//父级菜单的id
	private int ismenu;//显示顺序
	private long displayno;//显示的顺序
	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 long getDisplayno() {
		return displayno;
	}
	public void setDisplayno(long displayno) {
		this.displayno = displayno;
	}
	
	public Permission() {
		// TODO Auto-generated constructor stub
	}
	public Permission(long id, String name, String description, String url, long pid, int ismenu, long 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 + "]";
	}
	
	
}

PermissionDao方法

package com.zking.dao;

import java.util.ArrayList;
import java.util.Iterator;
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_easyui_permission";
		return super.executeQuery(sql, Permission.class, pageBean);
	}
	
	public List> menus(Permission permission, PageBean pageBean) throws Exception {
		List> trees = new ArrayList>();
		//从数据库拿到的菜单数据，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());
			vo.setParentId(p.getPid()+"");//节点的父id
			trees.add(vo);
		}
		return BuildTree.buildList(trees, "0");
	}
	
	
	
}

permissionDaoTest 测试

package com.zking.dao;

import static org.junit.Assert.*;

import java.util.List;

import org.junit.Test;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.zking.entity.Permission;
import com.zking.util.TreeVo;

public class PermissionDaoTest {

	private PermissionDao dao = new PermissionDao();
	
	@Test
	public void testList()  {
		try {
			List list = dao.list(null, null);
			for (Permission permission : list) {
//				System.out.println(permission);
			}
			ObjectMapper om = new ObjectMapper();
			System.out.println(om.writeValueAsString(list));
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	
	@Test
	public void testMenus()  {
		try {
			List> list = dao.menus(null, null);
			for (TreeVo permission : list) {
				System.out.println(permission);
			}
			ObjectMapper om = new ObjectMapper();
			System.out.println(om.writeValueAsString(list));
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

三、后台构建父子关系

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;
	}

}

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();
	}

}

package com.zking.dao;

import java.util.ArrayList;
import java.util.Iterator;
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_easyui_permission";
		return super.executeQuery(sql, Permission.class, pageBean);
	}
	
	public List> menus(Permission permission, PageBean pageBean) throws Exception {
		List> trees = new ArrayList>();
		//从数据库拿到的菜单数据，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());
			vo.setParentId(p.getPid()+"");//节点的父id
			trees.add(vo);
		}
		return BuildTree.buildList(trees, "-1");
	}
	
}

四、前端实现

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 permissiondao = new permissionDao();
	@Override
	public Permission getModel() {
		return permission;
	}
	
	
	public String menus(HttpServletRequest req, HttpServletResponse resp) {
		try {
			List> menus = permissiondao.menus(null, null);
			//向前端响应数据
			ResponseUtil.writeJson(resp, menus);
		} catch (Exception e) {
			e.printStackTrace();
		}
		return null;
	}

}

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




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