JAVA后台转换成树结构数据返回给前端

我们会经常用到树形，那么树形结构的数据是在前端做还是在后台做呢？我自己用过前端的ztree,selectTree等这些属于前端的组件，后台只需要把一个表的所有数据返回给前段就可以，前端可以通过id,pid来把层级结构划分，要是我们前端需要后台直接返回树结构数据怎么办，那么接下来我给大家介绍一下我写过的例子。

我们先看一张图了解一下树结构：我这里随便找一张图了解一下即可

接下来我们看一下数据，主要包括id,pid，名称

接下来我们写一个小例子，用递归方式转换为数

实体：

package cn.ccccltd.ccccoi.mediumterminvestment.domain;

import java.io.Serializable;
import java.util.List;

/**
 * @Description:返回前端，业务模块
 * @author yujiaqi
 * @date: 2019年9月9日下午2:07:19
 */
public class ProjectBasicInfoDTO implements Serializable {

    private static final long serialVersionUID = 1L;

    private String id;
    private String pId;
    private String key;
    private String title;
    private String value;
    private List<ProjectBasicInfoDTO> children;
    private Boolean selectable;
    private Boolean disableCheckbox;
    private Boolean disabled;
   
    
    public String getId() {
        return id;
    }
    public String getValue() {
        return value;
    }
    public void setValue(String value) {
        this.value = value;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getpId() {
        return pId;
    }
    public void setpId(String pId) {
        this.pId = pId;
    }
    public String getKey() {
        return key;
    }
    public void setKey(String key) {
        this.key = key;
    }
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }
    public List<ProjectBasicInfoDTO> getChildren() {
        return children;
    }
    public void setChildren(List<ProjectBasicInfoDTO> children) {
        this.children = children;
    }
    public Boolean getSelectable() {
        return selectable;
    }
    public void setSelectable(Boolean selectable) {
        this.selectable = selectable;
    }
    
    public Boolean getDisableCheckbox() {
        return disableCheckbox;
    }
    public void setDisableCheckbox(Boolean disableCheckbox) {
        this.disableCheckbox = disableCheckbox;
    }
    public Boolean getDisabled() {
        return disabled;
    }
    public void setDisabled(Boolean disabled) {
        this.disabled = disabled;
    }
    public static long getSerialversionuid() {
        return serialVersionUID;
    }
}

service实现类

 /**
     * 查询投资项目资金来源
     */
     @Override
     public List<ProjectBasicInfoDTO> queryFundingSource() {
         //查询投资项目资金来源
         List<DictionaryBean> list = projectBasicInfoMapper.queryDictionaryBean(Constant.FUNDING_SOURCE,Constant.DELFLAG);
         List<ProjectBasicInfoDTO> dataProcessing = ProjectBasicInfoServiceImpl.dataProcessing(list);
         List<ProjectBasicInfoDTO> buildByRecursive = TreeUtils.buildByRecursive(dataProcessing);
         return buildByRecursive;
     }
    
   
    /**
     * 将字典数据遍历放入ProjectBasicInfoDTO实体中
     * @param list
     * @return
     */
   public static List<ProjectBasicInfoDTO> dataProcessing(List<DictionaryBean> list){
       List<ProjectBasicInfoDTO> list1 = Lists.newArrayList();
       for (DictionaryBean dictionaryBean : list) {
           ProjectBasicInfoDTO projectBasicInfoDTO = new ProjectBasicInfoDTO();
           projectBasicInfoDTO.setId(dictionaryBean.getItemId());
           projectBasicInfoDTO.setpId(dictionaryBean.getItemParentId());
           projectBasicInfoDTO.setKey(dictionaryBean.getItemId());
           projectBasicInfoDTO.setTitle(dictionaryBean.getItemFullName());
           projectBasicInfoDTO.setValue(dictionaryBean.getItemFullName());
           projectBasicInfoDTO.setSelectable(false);
           projectBasicInfoDTO.setDisableCheckbox(true);
           projectBasicInfoDTO.setDisabled(true);
           list1.add(projectBasicInfoDTO);
       }
       return list1;
   }

递归方法工具类

package cn.ccccltd.ccccoi.mediumterminvestment.util;

import java.util.ArrayList;
import java.util.List;

import cn.ccccltd.ccccoi.mediumterminvestment.domain.ProjectBasicInfoDTO;

public class TreeUtils {
    /**
     * 使用递归方法建树
     * @param treeNodes
     * @return
     */
    public static List<ProjectBasicInfoDTO> buildByRecursive(List<ProjectBasicInfoDTO> projectBasicInfoDTOs) {
        List<ProjectBasicInfoDTO> trees = new ArrayList<ProjectBasicInfoDTO>();
        for (ProjectBasicInfoDTO projectBasicInfoDTO : projectBasicInfoDTOs) {
            if ("".equals(projectBasicInfoDTO.getpId()) || projectBasicInfoDTO.getpId() == null ) {
                trees.add(findChildren(projectBasicInfoDTO,projectBasicInfoDTOs));
            }
        }
        return trees;
    }
    
    /**
    * 递归查找子节点
    * @param treeNodes
    * @return
    */
    public static ProjectBasicInfoDTO findChildren(ProjectBasicInfoDTO projectBasicInfoDTO,List<ProjectBasicInfoDTO> projectBasicInfoDTOs) {
        for (ProjectBasicInfoDTO projectBasicInfoDTO2 : projectBasicInfoDTOs) {
            if(projectBasicInfoDTO.getId().equals(projectBasicInfoDTO2.getpId())) {
                if(projectBasicInfoDTO.getChildren() == null) {
                    projectBasicInfoDTO.setChildren(new ArrayList<ProjectBasicInfoDTO>());
                }
                //是否还有子节点，如果有的话继续往下遍历，如果没有则直接返回
                projectBasicInfoDTO.getChildren().add(findChildren(projectBasicInfoDTO2,projectBasicInfoDTOs));
            }
        }
        return projectBasicInfoDTO;
    }
}

树结构效果图

以上为后台处理树结构小demo,重点为递归那个工具类