首先看看两种树形菜单结构的代码示例。

SingleTreeNode：

package com.zzj.tree;public class SingleTreeNode { private int id; private int pId; private String name; public SingleTreeNode() { } public SingleTreeNode(int id, int pId, String name) { this.id = id; this.pId = pId; this.name = name; } public int getId() { return id; } public void setId(int id) { this.id = id; } public int getpId() { return pId; } public void setpId(int pId) { this.pId = pId; } public String getName() { return name; } public void setName(String name) { this.name = name; } @Override public String toString() { return "SingleTreeNode [id=" + id + ", pId=" + pId + ", name=" + name + "]"; }}

这种结构很适合存储到关系型数据库中。

MultiTreeNode：

package com.zzj.tree;import java.util.List;public class MultiTreeNode { private int id; private String name; private List<MultiTreeNode> children; public MultiTreeNode() { } public MultiTreeNode(int id, String name) { this.id = id; this.name = name; } public MultiTreeNode(int id, String name, List<MultiTreeNode> children) { this.id = id; this.name = name; this.children = children; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public List<MultiTreeNode> getChildren() { return children; } public void setChildren(List<MultiTreeNode> children) { this.children = children; } @Override public String toString() { return "MultiTreeNode [id=" + id + ", name=" + name + ", children=" + children + "]"; }}

两种转换器

ToMultiTreeTransformer：

package com.zzj.tree;import java.util.ArrayList;import java.util.List;public class ToMultiTreeTransformer { private List<SingleTreeNode> singleTreeNodes; private List<MultiTreeNode> multiTreeNodes = new ArrayList<>(); public ToMultiTreeTransformer(List<SingleTreeNode> singleTreeNodes) { this.singleTreeNodes = singleTreeNodes; } public List<MultiTreeNode> transform(){ // 先找出所有的根节点 for (int i = 0; i < singleTreeNodes.size(); i++) { SingleTreeNode singleTreeNode = singleTreeNodes.get(i); Boolean isRoot = true; for (int j = 0; j < singleTreeNodes.size(); j++) { SingleTreeNode temp = singleTreeNodes.get(j); if (singleTreeNode.getpId() == temp.getId()) { isRoot = false; break; } } if (isRoot) { MultiTreeNode multiTreeNode = new MultiTreeNode(singleTreeNode.getId(), singleTreeNode.getName()); multiTreeNodes.add(multiTreeNode); } } // 设置子节点 for (int i = 0; i < multiTreeNodes.size(); i++) { MultiTreeNode multiTreeNode = multiTreeNodes.get(i); setChildren(multiTreeNode); } return multiTreeNodes; } /** * 设置子节点 * @param multiTreeNode */ private void setChildren(MultiTreeNode multiTreeNode){ for (int j = 0; j < singleTreeNodes.size(); j++) { SingleTreeNode temp = singleTreeNodes.get(j); if (temp.getpId() == multiTreeNode.getId()) { MultiTreeNode child = new MultiTreeNode(temp.getId(), temp.getName()); List<MultiTreeNode> children = multiTreeNode.getChildren(); if (children == null) { children = new ArrayList<>(); multiTreeNode.setChildren(children); } children.add(child); setChildren(child); } } }}

ToSingleTreeTransformer：

package com.zzj.tree;import java.util.ArrayList;import java.util.List;public class ToSingleTreeTransformer { private List<MultiTreeNode> multiTreeNodes; private List<SingleTreeNode> singleTreeNodes = new ArrayList<>(); public ToSingleTreeTransformer(List<MultiTreeNode> multiTreeNodes) { this.multiTreeNodes = multiTreeNodes; } public List<SingleTreeNode> transform(){ // 先获取根节点 for (int i = 0; i < multiTreeNodes.size(); i++) { MultiTreeNode multiTreeNode = multiTreeNodes.get(i); SingleTreeNode singleTreeNode = new SingleTreeNode(multiTreeNode.getId(), 0, multiTreeNode.getName()); singleTreeNodes.add(singleTreeNode); } // 获取子节点 for (int i = 0; i < multiTreeNodes.size(); i++) { MultiTreeNode multiTreeNode = multiTreeNodes.get(i); getChildren(multiTreeNode); } return singleTreeNodes; } /** * 获取子节点 * @param multiTreeNode */ private void getChildren(MultiTreeNode multiTreeNode){ for (int i = 0; i < singleTreeNodes.size(); i++) { SingleTreeNode temp = singleTreeNodes.get(i); if (multiTreeNode.getId() == temp.getId()) { List<MultiTreeNode> children = multiTreeNode.getChildren(); if (children != null) { for (int j = 0; j < children.size(); j++) { MultiTreeNode child = children.get(j); SingleTreeNode singleTreeNode = new SingleTreeNode(child.getId(), multiTreeNode.getId(), child.getName()); singleTreeNodes.add(singleTreeNode); getChildren(child); } } } } }}

测试

package com.zzj.tree;import java.util.ArrayList;import java.util.List;public class TreeTransformerTest { private final static List<SingleTreeNode> SINGLE_TREE = new ArrayList<SingleTreeNode>(); static { SingleTreeNode China = new SingleTreeNode(1, 0, "中国"); SINGLE_TREE.add(China); SingleTreeNode Hunan = new SingleTreeNode(2, 1, "湖南"); SINGLE_TREE.add(Hunan); SingleTreeNode Changsha = new SingleTreeNode(3, 2, "长沙"); SINGLE_TREE.add(Changsha); SingleTreeNode Hubei = new SingleTreeNode(4, 1, "湖北"); SINGLE_TREE.add(Hubei); SingleTreeNode Wuhan = new SingleTreeNode(5, 4, "武汉"); SINGLE_TREE.add(Wuhan); SingleTreeNode America = new SingleTreeNode(6, 0, "美国"); SINGLE_TREE.add(America); SingleTreeNode California = new SingleTreeNode(7, 6, "加利福尼亚"); SINGLE_TREE.add(California); SingleTreeNode LosAngeles = new SingleTreeNode(8, 7, "洛杉矶"); SINGLE_TREE.add(LosAngeles); } public static void main(String[] args) throws Exception { ToMultiTreeTransformer multiTreeTransformer = new ToMultiTreeTransformer(SINGLE_TREE); List<MultiTreeNode> multiTreeNodes = multiTreeTransformer.transform(); System.out.println(multiTreeNodes); ToSingleTreeTransformer singleTreeTransformer = new ToSingleTreeTransformer(multiTreeNodes); List<SingleTreeNode> singleTreeNodes = singleTreeTransformer.transform(); System.out.println(singleTreeNodes); }}

输出结果：

[MultiTreeNode [id=1, name=中国, children=[MultiTreeNode [id=2, name=湖南, children=[MultiTreeNode [id=3, name=长沙, children=null]]], MultiTreeNode [id=4, name=湖北, children=[MultiTreeNode [id=5, name=武汉, children=null]]]]], MultiTreeNode [id=6, name=美国, children=[MultiTreeNode [id=7, name=加利福尼亚, children=[MultiTreeNode [id=8, name=洛杉矶, children=null]]]]]] [SingleTreeNode [id=1, pId=0, name=中国], SingleTreeNode [id=6, pId=0, name=美国], SingleTreeNode [id=2, pId=1, name=湖南], SingleTreeNode [id=3, pId=2, name=长沙], SingleTreeNode [id=4, pId=1, name=湖北], SingleTreeNode [id=5, pId=4, name=武汉], SingleTreeNode [id=7, pId=6, name=加利福尼亚], SingleTreeNode [id=8, pId=7, name=洛杉矶]]

总结

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