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 <T> List<T> getTree(List<T> 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<T> 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 <T> void fillTree(List<T> parentList, List<T> originalList, String keyName, String parentFieldName, String childrenFieldName) throws Exception {
for (int i = 0; i < parentList.size(); i++) {
List<T> 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 <T> List<T> fillChildren(T parent, List<T> originalList, String keyName, String parentFieldName, String childrenFieldName) throws Exception {
List<T> 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
*/
@Test
public void ListToMap() throws Exception {
List<Catalog> 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<Catalog> 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("-", "");
}