把列表转换为树结构

/** * 把列表转换为树结构 * * @param originalList 原始list数据 * @param keyName 作为唯一标示的字段名称 * @return 组装后的集合 */public static 
     
       List
      
        getTree(List
       
         originalList, String keyName) throws Exception {    String parentFieldName = "parentId";    String childrenFieldName = "children";    // 获取根节点，即找出父节点为空的对象    List
        
          topList = new ArrayList<>();    for (int i = 0; i < originalList.size(); i++) {        T t = originalList.get(i);        String parentId = BeanUtils.getProperty(t, parentFieldName);        if (StringUtils.isBlank(parentId)) {            topList.add(t);        }    }    // 将根节点从原始list移除，减少下次处理数据    originalList.removeAll(topList);    // 递归封装树    fillTree(topList, originalList, keyName, parentFieldName, childrenFieldName);    return topList;}
        
       
      
     

 

封装树

/** * 封装树 * * @param parentList 要封装为树的父对象集合 * @param originalList 原始list数据 * @param keyName 作为唯一标示的字段名称 * @param parentFieldName 模型中作为parent字段名称 * @param childrenFieldName 模型中作为children的字段名称 */public static 
     
       void fillTree(List
      
        parentList, List
       
         originalList, String keyName, String parentFieldName, String childrenFieldName) throws Exception {    for (int i = 0; i < parentList.size(); i++) {        List
        
          children = fillChildren(parentList.get(i), originalList, keyName, parentFieldName, childrenFieldName);        if (children.isEmpty()) {            continue;        }        originalList.removeAll(children);        fillTree(children, originalList, keyName, parentFieldName, childrenFieldName);    }}
        
       
      
     

封装子对象

/** * 封装子对象 * * @param parent 父对象 * @param originalList 待处理对象集合 * @param keyName 作为唯一标示的字段名称 * @param parentFieldName 模型中作为parent字段名称 * @param childrenFieldName 模型中作为children的字段名称 */public static 
     
       List
      
        fillChildren(T parent, List
       
         originalList, String keyName, String parentFieldName, String childrenFieldName) throws Exception {    List
        
          childList = new ArrayList<>();    String parentId = BeanUtils.getProperty(parent, keyName);    for (int i = 0; i < originalList.size(); i++) {        T t = originalList.get(i);        String childParentId = BeanUtils.getProperty(t, parentFieldName);        if (parentId.equals(childParentId)) {            childList.add(t);        }    }    if (!childList.isEmpty()) {        FieldUtils.writeDeclaredField(parent, childrenFieldName, childList, true);    }    return childList;}
        
       
      
     

 

测试实体类

/** * 测试实体类 */public class Catalog {    /**     * 唯一编号 uuid     */    private String id;    /**     * 名称     */    private String name;    /**     * 父节点id     */    private String parentId;    /**     * 子节点(数据库中不存在该字段，仅用于传输数据使用)     */    private List
      children;    // 省略 get set}

测试

/*** 测试 一共有六个Catalog* 其中：name1下面有三个子节点：name2、name3、name4*      name2下面有两个子节点：name5、name6*/@Testpublic void ListToMap() throws Exception {    List
     
       list = new ArrayList<>();    Catalog catalog = new Catalog();    String flowId = randomUUID();    catalog.setFlowId(flowId);    catalog.setName("name1");    list.add(catalog);    catalog = new Catalog();    String flowId2 = randomUUID();    catalog.setFlowId(flowId2);    catalog.setName("name2");    catalog.setParentId(flowId);    list.add(catalog);    catalog = new Catalog();    String flowId3 = randomUUID();    catalog.setFlowId(flowId3);    catalog.setName("name3");    catalog.setParentId(flowId);    list.add(catalog);    catalog = new Catalog();    String flowId4 = randomUUID();    catalog.setFlowId(flowId4);    catalog.setName("name4");    catalog.setParentId(flowId);    list.add(catalog);    catalog = new Catalog();    String flowId5 = randomUUID();    catalog.setFlowId(flowId5);    catalog.setName("name5");    catalog.setParentId(flowId2);    list.add(catalog);    catalog = new Catalog();    String flowId6 = randomUUID();    catalog.setFlowId(flowId6);    catalog.setName("name6");    catalog.setParentId(flowId2);    list.add(catalog);    List
      
        tree = getTree(list, "flowId");    System.out.println(JSON.toJSONString(tree));    /* 装换后输出json样式    [      {        "id" : "ee55dafee60d44a3a143bd3623f29aa9",        "name" : "name1",        "children" : [          {            "id" : "2e049bdb67624054ad989b511f1b7674",            "parentId" : "ee55dafee60d44a3a143bd3623f29aa9",            "name" : "name2",            "children" : [              {                "id" : "9292a15c7a5e4983ac03d10c5fe12a14",                "name" : "name5",                "parentId" : "2e049bdb67624054ad989b511f1b7674"              },              {                "id" : "6cd9608726a1438682f239b6017680ca",                "name" : "name6",                "parentId" : "2e049bdb67624054ad989b511f1b7674"              }            ]          },          {            "id" : "98e90c9e23e445f980c4116bd4c83233",            "name" : "name3",            "parentId" : "ee55dafee60d44a3a143bd3623f29aa9"          },          {            "id" : "5e67e73c6aef4eb19b63b4789dcc3486",            "name" : "name4",            "parentId" : "ee55dafee60d44a3a143bd3623f29aa9"          }        ]      }    ]    */}protected String randomUUID() {    return UUID.randomUUID().toString().replace("-", "");}