java 递归拼接树形结构代码

1、json数据（目标）

[{
          label: '一级 1',
          children: [{
            label: '二级 1-1',
            children: [{
              label: '三级 1-1-1'
            }]
          }]
        }, {
          label: '一级 2',
          children: [{
            label: '二级 2-1',
            children: [{
              label: '三级 2-1-1'
            }]
          }, {
            label: '二级 2-2',
            children: [{
              label: '三级 2-2-1'
            }]
          }]
        }, {
          label: '一级 3',
          children: [{
            label: '二级 3-1',
            children: [{
              label: '三级 3-1-1'
            }]
          }, {
            label: '二级 3-2',
            children: [{
              label: '三级 3-2-1'
            }]
          }]
        }]

2、基础类型

package test;

import java.util.List;

/**
 * chao
 */
public class DataItem {
    private String label;

    private List<DataItem> children;

    public String getLabel() {
        return label;
    }

    public void setLabel(String label) {
        this.label = label;
    }

    public List<DataItem> getChildren() {
        return children;
    }

    public void setChildren(List<DataItem> children) {
        this.children = children;
    }
}

package test;

/**
 * 代表数据库里的表
 */
public class DataModel {
    private  Integer id;
    private  String label;
    private  Integer pId;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getLabel() {
        return label;
    }

    public void setLabel(String label) {
        this.label = label;
    }

    public Integer getPId() {
        return pId;
    }

    public void setPId(Integer pId) {
        this.pId = pId;
    }

    public DataModel(Integer id, String label, Integer pId) {
        this.id = id;
        this.label = label;
        this.pId = pId;
    }
}

3、手动拼接树形结构

// 手动拼接json格式
        {
            List<DataItem> list = new ArrayList<DataItem>();
            //第一条数据
            {
                DataItem data = new DataItem();
                data.setLabel("一级 1");
                List<DataItem> data_child = new ArrayList<DataItem>();
                data.setChildren(data_child);

                DataItem data_child_Data1 = new DataItem();
                data_child_Data1.setLabel("二级 1-1");
                List<DataItem> data_child_Data1_child = new ArrayList<DataItem>();
                data_child_Data1.setChildren(data_child_Data1_child);

                data_child.add(data_child_Data1);

                DataItem child1Data1_child_Data1 = new DataItem();
                child1Data1_child_Data1.setLabel("三级 1-1-1");
                data_child_Data1_child.add(child1Data1_child_Data1);

                list.add(data);
            }

            //第二条数据
            {
                DataItem data = new DataItem();
                data.setLabel("一级 2");
                List<DataItem> data_child = new ArrayList<DataItem>();
                data.setChildren(data_child);
                //第一条
                {
                    DataItem data_child_Data1 = new DataItem();
                    data_child_Data1.setLabel("二级 2-1");
                    List<DataItem> data_child_Data1_child = new ArrayList<DataItem>();
                    data_child_Data1.setChildren(data_child_Data1_child);

                    data_child.add(data_child_Data1);

                    DataItem child1Data1_child_Data1 = new DataItem();
                    child1Data1_child_Data1.setLabel("三级 2-1-1");
                    data_child_Data1_child.add(child1Data1_child_Data1);
                }

                //第二条
                {
                    DataItem data_child_Data1 = new DataItem();
                    data_child_Data1.setLabel("二级 2-2");
                    List<DataItem> data_child_Data1_child = new ArrayList<DataItem>();
                    data_child_Data1.setChildren(data_child_Data1_child);

                    data_child.add(data_child_Data1);

                    DataItem child1Data1_child_Data1 = new DataItem();
                    child1Data1_child_Data1.setLabel("三级 2-2-1");
                    data_child_Data1_child.add(child1Data1_child_Data1);
                }

                list.add(data);
            }


            //第三条数据
            {
                DataItem data = new DataItem();
                data.setLabel("一级 3");
                List<DataItem> data_child = new ArrayList<DataItem>();
                data.setChildren(data_child);
                //第一条
                {
                    DataItem data_child_Data1 = new DataItem();
                    data_child_Data1.setLabel("二级 3-1");
                    List<DataItem> data_child_Data1_child = new ArrayList<DataItem>();
                    data_child_Data1.setChildren(data_child_Data1_child);

                    data_child.add(data_child_Data1);

                    DataItem child1Data1_child_Data1 = new DataItem();
                    child1Data1_child_Data1.setLabel("三级 3-1-1");
                    data_child_Data1_child.add(child1Data1_child_Data1);
                }

                //第二条
                {
                    DataItem data_child_Data1 = new DataItem();
                    data_child_Data1.setLabel("二级 3-2");
                    List<DataItem> data_child_Data1_child = new ArrayList<DataItem>();
                    data_child_Data1.setChildren(data_child_Data1_child);

                    data_child.add(data_child_Data1);

                    DataItem child1Data1_child_Data1 = new DataItem();
                    child1Data1_child_Data1.setLabel("三级 3-2-1");
                    data_child_Data1_child.add(child1Data1_child_Data1);
                }

                list.add(data);
            }

            System.out.println("----------手动拼接----------");
            System.out.println(JSON.toJSONString(list));

4、递归拼接

//原始数据
            List<DataModel> dataList = new ArrayList();
            {
                dataList.add(new DataModel(1, "一级 1", 0));
                dataList.add(new DataModel(2, "二级 1-1", 1));
                dataList.add(new DataModel(3, "三级 1-1-1", 2));

                dataList.add(new DataModel(4, "一级 2", 0));
                dataList.add(new DataModel(5, "二级 2-1", 4));
                dataList.add(new DataModel(6, "三级 2-1-1", 5));
                dataList.add(new DataModel(7, "二级 2-2", 4));
                dataList.add(new DataModel(8, "三级 2-2-1", 7));

                dataList.add(new DataModel(9, "一级 3", 0));
                dataList.add(new DataModel(10, "二级 3-1", 9));
                dataList.add(new DataModel(11, "三级 3-1-1", 10));
                dataList.add(new DataModel(12, "二级 3-2", 9));
                dataList.add(new DataModel(13, "三级 3-2-1", 12));
            }

            //树结构结果
            List<DataItem> treeList = new ArrayList<DataItem>();
            treeList = GetTreeData(dataList, 0);

            System.out.println("----------递归拼接----------");
            System.out.println(JSON.toJSONString(treeList));

 /**
     * 递归
     *
     * @param sourceDataList
     * @param pId
     * @return
     */
    private static List<DataItem> GetTreeData(List<DataModel> sourceDataList, Integer pId) {
        List<DataItem> returnList = new ArrayList<DataItem>();
        for (Integer i = 0; i < sourceDataList.size(); i++) {
            DataModel itemData = sourceDataList.get(i);
            if (itemData.getPId().equals(pId)) {
                DataItem item = new DataItem();
                item.setLabel(itemData.getLabel());
                List children = GetTreeData(sourceDataList, itemData.getId());
                if (children.size() > 0)
                    item.setChildren(children);
                returnList.add(item);
            }
        }
        return returnList;
    }