在学习谷粒mall过程中发现一个问题，mysql存储三级菜单时，发现主方法（listWithTree()）和递归方法（getChildrens()）中都要用sorted()方法，本以为在listWithTree（）用一次sorted()即可，然后做了测试模拟场景
原代码
@Override
public List<CategoryEntity> listWithTree() {
//1.查出所有分类
List<CategoryEntity> entities = baseMapper.selectList(null);
//2.组装成父子的树形结构
//1)找到一级分类
List<CategoryEntity> level1Menus = entities.stream().filter(categoryEntity ->
categoryEntity.getParentCid() == 0
).map(menu->{
menu.setChildren(getChildrens(menu,entities));
return menu;
//排序
}).sorted((menu1,menu2)->{
return (menu1.getSort()==null?0:menu1.getSort())-(menu2.getSort()==null?0:menu2.getSort());
}).collect(Collectors.toList());
return level1Menus;
}
//递归查找菜单的子菜单
private List<CategoryEntity> getChildrens(CategoryEntity root,List<CategoryEntity> all){
List<CategoryEntity> children = all.stream().filter(CategoryEntity -> {
return CategoryEntity.getParentCid() == root.getCatId();
}).map(CategoryEntity->{
//找到子菜单
CategoryEntity.setChildren(getChildrens(CategoryEntity,all));
return CategoryEntity;
//排序
}).sorted((menu1,menu2)->{
return (menu1.getSort()==null?0:menu1.getSort())-(menu2.getSort()==null?0:menu2.getSort());
}).collect(Collectors.toList());
return children;
}
这里对db查询后的集合数据进行处理，所有流都进行排序，结果正常
模拟场景进行测试
private static void test() {
//模拟数据
Node e0 = new Node().setId(1L).setPid(0L).setSort(7);
Node e1 = new Node().setId(2L).setPid(1L).setSort(6);
Node e2 = new Node().setId(3L).setPid(1L).setSort(5);
Node e3 = new Node().setId(4L).setPid(2L).setSort(4);
Node e4 = new Node().setId(5L).setPid(2L).setSort(3);
Node e5 = new Node().setId(6L).setPid(3L).setSort(2);
Node e6 = new Node().setId(7L).setPid(3L).setSort(1);
ArrayList<Node> e2_chilren = new ArrayList<>();
e2_chilren.add(e5);
e2_chilren.add(e6);
e2.setChildrenList(e2_chilren);
ArrayList<Node> e1_chilren = new ArrayList<>();
e1_chilren.add(e3);
e1_chilren.add(e4);
e1.setChildrenList(e1_chilren);
ArrayList<Node> e0_chilren = new ArrayList<>();
e0_chilren.add(e1);
e0_chilren.add(e2);
e0.setChildrenList(e0_chilren);
ArrayList<Node> nodes = new ArrayList<>();
nodes.add(e0);
nodes.add(e1);
nodes.add(e2);
nodes.add(e3);
nodes.add(e4);
nodes.add(e5);
nodes.add(e6);
//查看模拟数据是否正确
// for (Entity entity : entities) {
// System.out.println(entity);
// }
List<Node> result = nodes.stream().filter(node ->
node.getPid() == 0
).map(node->{
node.setChildrenList(getChildrens(node,nodes));
return node;
}).sorted((node1,node2)->{
return (node1.getSort()==null?0:node1.getSort())-(node2.getSort()==null?0:node2.getSort());
}).collect(Collectors.toList());
//打印排序后的结果
System.out.println(result);
}
//递归查找菜单的子菜单
private static List<Node> getChildrens(Node root,List<Node> all) {
List<Node> children = all.stream().filter(node -> {
return node.getPid() == root.getId();
}).map(node -> {
//找到子菜单
node.setChildrenList(getChildrens(node, all));
return node;
}).sorted((node1,node2)->{
//菜单排序
return (node1.getSort()==null?0:node1.getSort())-(node2.getSort()==null?0:node2.getSort());
}).collect(Collectors.toList());
return children;
}
结果为
[Entity(id=1, pid=0, sort=7, children=[
Entity(id=2, pid=1, sort=6, children=[
Entity(id=4, pid=2, sort=4, children=[]),
Entity(id=5, pid=2, sort=3, children=[])]),
Entity(id=3, pid=1, sort=5, children=[
Entity(id=6, pid=3, sort=2, children=[]),
Entity(id=7, pid=3, sort=1, children=[])])])]
展示成xml
<node id="1" pid="0">
<node id="2" pid="1">
<node id="4" pid="2"/>
<node id="5" pid="2"/>
</node>
<node id="3" pid="1">
<node id="6" pid="3"/>
<node id="7" pid="3"/>
</node>
</node>
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- 5
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- 7
结果显示正常。
接着注释以下代码后运行
//递归查找菜单的子菜单
private static List<Node> getChildrens(Node root,List<Node> all) {
List<Node> children = all.stream().filter(node -> {
return node.getPid() == root.getId();
}).map(node -> {
//找到子菜单
node.setChildrenList(getChildrens(node, all));
return node;
})
/*.sorted((node1,node2)->{
//菜单排序
return (node1.getSort()==null?0:node1.getSort())-(node2.getSort()==null?0:node2.getSort());
})*/.collect(Collectors.toList());
return children;
}
结果为
[Node(id=1, pid=0, sort=7, children=[
Node(id=3, pid=1, sort=5, children=[
Node(id=7, pid=3, sort=1, children=[]),
Node(id=6, pid=3, sort=2, children=[])]),
Node(id=2, pid=1, sort=6, children=[
Node(id=5, pid=2, sort=3, children=[]),
Node(id=4, pid=2, sort=4, children=[])])])]
展示为xml
<node id="1" pid="0">
<node id="3" pid="1">
<node id="7" pid="3"/>
<node id="6" pid="3"/>
</node>
<node id="2" pid="1">
<node id="5" pid="2"/>
<node id="4" pid="2"/>
</node>
</node>
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- 6
- 2 - 5
- 4
结果显示没有完成排序，说明每次使用流都要进行排序。