JAVA后台转换成树结构数据返回给前端的实现方法

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

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