前言：在做java web项目时，前端控件例如国家-省-市-区-县等树形列表，常常需要多级树形json数据，例如：
[ { "name": "商品目录", "pid": "-1", "id": "1", "children": [ { "name": "日用品", "pid": "1", "id": "11", "children": [ { "name": "洗发水", "pid": "11", "id": "111", "children": [ { "name": "霸王", "pid": "111", "id": "1111", "children": [] } ] } ] }, { "name": "食品", "pid": "1", "id": "12", "children": [] } ] } ]
整体思路分为两步，第一步获取目录及其所有子目录，获取后的列表形式如下：
[ {"id":"1","pid":"-1","name":"商品目录"}, {"id":"11","pid":"1","name":"日用品"}, {"id":"12","pid":"1","name":"食品"}, {"id":"111","pid":"11","name":"洗发水"}, {"id":"1111","pid":"111","name":"霸王"} ]
第二步，利用递归思想拼装该数据，拼装方法的工具类如下：
package *.*.*; import net.sf.json.JSONArray; import java.util.ArrayList; import java.util.List; /** * 构造目录JSON树 * Created by fukang on 2017/5/26 0026. */ public class TreeBuilder { List<Node> nodes = new ArrayList<>(); public String buildTree(List<Node> nodes) { TreeBuilder treeBuilder = new TreeBuilder(nodes); return treeBuilder.buildJSONTree(); } public TreeBuilder() { } public TreeBuilder(List<Node> nodes) { super(); this.nodes = nodes; } // 构建JSON树形结构 public String buildJSONTree() { List<Node> nodeTree = buildTree(); JSONArray jsonArray = JSONArray.fromObject(nodeTree); return jsonArray.toString(); } // 构建树形结构 public List<Node> buildTree() { List<Node> treeNodes = new ArrayList<>(); List<Node> rootNodes = getRootNodes(); for (Node rootNode : rootNodes) { buildChildNodes(rootNode); treeNodes.add(rootNode); } return treeNodes; } // 递归子节点 public void buildChildNodes(Node node) { List<Node> children = getChildNodes(node); if (!children.isEmpty()) { for (Node child : children) { buildChildNodes(child); } node.setChildren(children); } } // 获取父节点下所有的子节点 public List<Node> getChildNodes(Node pnode) { List<Node> childNodes = new ArrayList<>(); for (Node n : nodes) { if (pnode.getId().equals(n.getPid())) { childNodes.add(n); } } return childNodes; } // 判断是否为根节点 public boolean rootNode(Node node) { boolean isRootNode = true; for (Node n : nodes) { if (node.getPid().equals(n.getId())) { isRootNode = false; break; } } return isRootNode; } // 获取集合中所有的根节点 public List<Node> getRootNodes() { List<Node> rootNodes = new ArrayList<>(); for (Node n : nodes) { if (rootNode(n)) { rootNodes.add(n); } } return rootNodes; } public static class Node { private String id; private String pid; private String name; private List<Node> children; public Node() { } public Node(String id, String pid, String name) { super(); this.id = id; this.pid = pid; this.name = name; } public String getId() { return id; } public void setId(String id) { this.id = id; } public String getPid() { return pid; } public void setPid(String pid) { this.pid = pid; } public String getName() { return name; } public void setName(String name) { this.name = name; } public List<Node> getChildren() { return children; } public void setChildren(List<Node> children) { this.children = children; } } }
在Controller中的调用方法是：
@RequestMapping("/bulidJsonTree") @ResponseBody public String buildJsonTree(HttpServletRequest request) { // 获取全部目录节点 List<Node> nodes = iGoodsDirSvc.getAllDirList(); // 拼装树形json字符串 String json = new TreeBuilder().buildTree(nodes); return json; }
其中iGoodsDirSvc.getAllDirList()方法需要将取到的数据转为Node类型：
String hql = "select id as id,pId as pid,name as name from Directory"; Query query = factory.getCurrentSession().createQuery(hql) .setResultTransformer(Transformers.aliasToBean(TreeBuilder.Node.class)); return query.list();
其次、我认为最简便转换JSON的方法是：
import com.alibaba.fastjson.JSON; ......... System.out.println(JSON.toJSONString(树数据集合));
见笑了，见笑了。
