多级树形目录mysql的使用_利用java+mysql递归实现拼接树形JSON列表的方法示例
前言
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我们在做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 nodes = new ArrayList<>();
public String buildTree(List nodes) {
TreeBuilder treeBuilder = new TreeBuilder(nodes);
return treeBuilder.buildJSONTree();
}
public TreeBuilder() {
}
public TreeBuilder(List nodes) {
super();
this.nodes = nodes;
}
// 构建JSON树形结构
public String buildJSONTree() {
List nodeTree = buildTree();
JSONArray jsonArray = JSONArray.fromObject(nodeTree);
return jsonArray.toString();
}
// 构建树形结构
public List buildTree() {
List treeNodes = new ArrayList<>();
List rootNodes = getRootNodes();
for (Node rootNode : rootNodes) {
buildChildNodes(rootNode);
treeNodes.add(rootNode);
}
return treeNodes;
}
// 递归子节点
public void buildChildNodes(Node node) {
List 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 getChildNodes(Node pnode) {
List 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 getRootNodes() {
List 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 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 getChildren() {
return children;
}
public void setChildren(List 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 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();
总结
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