Java build tree menu, java build tree

Java build tree menu, java build tree

Build a tree menu

:Multi-level menus are supported.

Menu entity class:

Public class Menu {// Menu id private String id; // Menu name private String name; // parent Menu id private String parentId; // Menu url private String url; // Menu icon private String icon; // Menu order private int order; // sub-Menu private List <Menu> children ;//... the getter and setter methods and toString methods are omitted}

Menus generally need to be sorted. We sort the menus according to the order field of the Menu:

/** Sort by order */public Comparator <Menu> order () {Comparator <Menu> comparator = new Comparator <Menu> () {@ Override public int compare (Menu o1, Menu o2) {if (o1.getOrder ()! = O2.getOrder () {return o1.getOrder ()-o2.getOrder ();} return 0 ;}; return comparator ;}

Method of Generating tree:

Public Map <String, Object> findTree () {Map <String, Object> data = new HashMap <String, Object> (); try {// query all Menu lists <Menu> allMenu = menuDao. findTree (); // root node List <Menu> rootMenu = new ArrayList <Menu> (); for (Menu nav: allMenu) {if (nav. getParentId (). equals ("0") {// The parent node is 0, which is the root node. RootMenu. add (nav) ;}}/* sort by order of the Menu class */Collections. sort (rootMenu, order (); // you can specify a sub-Menu for the root Menu. getClild Is A Recursively called for (Menu nav: rootMenu) {/* obtain all subnodes under the root node using the getChild Method */List <Menu> childList = getChild (nav. getId (), allMenu); nav. setChildren (childList); // set a subnode for the root node}/*** output the constructed menu data. **/Data. put ("success", "true"); data. put ("list", rootMenu); return data;} catch (Exception e) {data. put ("success", "false"); data. put ("list", new ArrayList (); return data ;}}

Obtain the sub-menu:

/*** Get subnode ** @ param id parent node id * @ param allMenu all menu lists * @ return under each root node, list of all sub-menus */public List <Menu> getChild (String id, List <Menu> allMenu) {// sub-Menu List <Menu> childList = new ArrayList <Menu> (); for (Menu nav: allMenu) {// traverse all nodes, compare the parent id of all menus with the id of the passed root node // equal Description: it is the child node of the root node. If (nav. parentId (). equals (id) {childList. add (nav) ;}}// recursive for (Menu nav: childList) {nav. setChildren (getChild (nav. getId (), allMenu);} Collections. sort (childList, order (); // sort // if there are no subnodes under the node, an empty List is returned (recursively exiting) if (childList. size () = 0) {return new ArrayList <Menu> () ;}return childList ;}

The returned JSON string is as follows:

{"Success": "true", "list": [{"id": "1", "name": "Java", "parentid": "0 ", "url": "http://www.aliouchen.com", "order": 1, "children": [{"id": "2", "name": "concurrent programming ", "parentid": "1", "url": "http://www.aliouchen.com", "order": 1, "children": []}, {"id": "3 ", "name": "multithreading", "parentid": "1", "url": "http://www.aliouchen.com", "order": 2, "children": ["id ": "4", "name": "Thread", "parentid": "3", "url": "http://www.aliouchen.com", "order": 1,
"Children": []}] },{ "id": "5", "name": "Python", "parentid": "0", "url ": "http://www.aliouchen.com", "order": 2, "children": []}