从深层递归父子关系构建JSON
从深层递归父子关系构建JSON
提问于 2016-10-17 16:06:06
我在postgres数据库中有以下记录。parent_pk与父子关系中的主键相关。pk =1是所有子代的直接和间接的父代。
pk name type parent_pk
--- ---- ---- ---------
1 hnumber101 house 1
2 hnumber201 house 1
791 dodge_charger vehicle 1
801 mustang vehicle 791
595020 civic vehicle 2
10077661099 john user 10046725614
10046725614 mesto dev 1
801 shen house 791
44444444 crep house 10046725614
22222222 keper user 10046725614
11111111 show house 10046725614
84257651 shen house 801
11 lemp house 2我想用下面的格式从上面生成一个json -
{
"children" : [
{ "pk" : "1", "name" : "hnumber101", "children" : [
{ "pk" : "10046725614", "name" : "mesto", "children" : [
{ "pk" : "10077661099", "name" : "john", "children" : [] },
{ "pk" : "44444444", "name" : "crep", "children" : [] },
{ "pk" : "22222222", "name" : "keper", "children" : [] },
{ "pk" : "11111111", "name" : "show", "children" : [] }
] }
] },
{ "pk" : "791", "name" : "dodge_charger", "children" : [
{ "pk" : "801", "name" : "mustang", "children" : [
{ "pk" : "84257651", "name" : "shen", "children" : [
] }
] },
{ "pk" : "2", "name" : "hnumber201", "children" : [
{ "pk" : "595020", "name" : "civic", "children" : [] },
{ "pk" : "11", "name" : "lemp", "children" : [] }
] }
] }
] }
]
}用我现在的代码，我只能得到pk = 1的孩子的孩子，但是深度递归没有发生。
Collection<GatherEntity> gatherEntityChildren= gatherManager.findByParentGatherId(1);
getRecursiveGatherFromParent(gatherEntityChildren, gatherListParent);
private List<Gather> getRecursiveGatherFromParent(Collection<GatherEntity> gatherEntityChildren, List<Gather> gatherListParent) throws JSONException {
if(gatherEntityChildren != null && gatherEntityChildren.size() > 0) {
for (Iterator<gatherEntity> iterator = gatherEntityChildren.iterator(); iterator.hasNext();) {
GatherEntity gatherEntity = (GatherEntity) iterator.next();
Gather gather = getGatherFromEntity(gatherEntity);
List<Gather> gatherChildren = populateGatherAndChild(gatherEntity);
gather.setChildren(new HashSet<Gather>(gatherChildren));
gatherListParent.add(gather);
}
}
return gatherListParent;
}
private List<Gather> populateGatherAndChild(GatherEntity gatherEntity) {
Collection<GatherEntity> gatherEntityChildren= gatherManager.findByParentGatherId(gatherEntity.getGatherId());
List<Gather> gatherList = gatherEntityChildren.stream().map(UserAPIImpl::getGatherFromEntity).collect(Collectors.toList());
return gatherList;
}
private static Gather getGatherFromEntity(GatherEntity gatherEntity) {
Gather gather = new Gather();
gather.setGatherId(gatherEntity.getGatherId());
gather.setName(gatherEntity.getName());
return gather;
}Stack Overflow用户
发布于 2016-10-17 16:25:48
您错过了对子对象的递归调用：
if(gatherEntityChildren != null && gatherEntityChildren.size() > 0) {
for (Iterator<gatherEntity> iterator = gatherEntityChildren.iterator(); iterator.hasNext();) {
GatherEntity gatherEntity = (GatherEntity) iterator.next();
Gather gather = getGatherFromEntity(gatherEntity);
Collection<GatherEntity> gatherChildren = populateGatherAndChild(gatherEntity);
List<Gather> gatherList = gatherEntityChildren.stream().map(UserAPIImpl::getGatherFromEntity).collect(Collectors.toList());
gather.setChildren(new HashSet<Gather>(gatherList));
gatherListParent.add(gather);
getRecursiveGatherFromParent(gatherChildren, gatherListParent);
}
}
return gatherListParent;
}
private List<GatherEntity> populateGatherAndChild(GatherEntity gatherEntity) {
return gatherManager.findByParentGatherId(gatherEntity.getGatherId());
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/40081322
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