英文:
Java Stream: How to find id from json?
问题
我有一个以下的 JSON，以及一个与之类似的类 MyClient：
[
{
"id": 2,
"partners": [
{
"configuration": {
"connect-fleet-sync": false
},
"id": "cf89cbc5-0886-48cc-81e7-ca6123bc4857"
},
{
"configuration": {
"connect-fleet-sync": false
},
"id": "cf89cbc5-0886-48cc-81e7-ca6123bc4967"
}
]
},
{
"id": 3,
"partners": [
{
"configuration": {
"connect-fleet-sync": false
},
"id": "c3354af5-16e3-4713-b1f5-a5369c0b13d6"
}
]
}
]
我需要一个方法，它接收 UUID，然后返回 id。
例如 findClientId("cf89cbc5-0886-48cc-81e7-ca6123bc4967")，然后返回 2：
以下是我尝试过的代码：
public static void findClientId(String partnerId, MyClient[] allMyClients) {
Stream.of(allMyClients)
.map(MyClient::getPartners)
.forEach(partners ->
partners.stream()
.filter(partner -> partner.getId().equals(partnerId))
.map(Partner::getClientId)
.forEach(System.out::println)
);
}
但是它报错 Non-static method cannot be referenced from a static context，在 .forEach(Partner::getPartnerId) 这一行。
英文:
I have a json as below and a similar classes respect to it MyClient:
[
{
"id": 2,
"partners": [
{
"configuration": {
"connect-fleet-sync": false
},
"id": "cf89cbc5-0886-48cc-81e7-ca6123bc4857"
},
{
"configuration": {
"connect-fleet-sync": false
},
"id": "cf89cbc5-0886-48cc-81e7-ca6123bc4967"
}
]
},
{
"id": 3,
"partners": [
{
"configuration": {
"connect-fleet-sync": false
},
"id": "c3354af5-16e3-4713-b1f5-a5369c0b13d6"
}
]
}
]
I need a method which receives the uuid and it returns id.
Fr example findClientId("cf89cbc5-0886-48cc-81e7-ca6123bc4967") and then it returns 2:
Here is what i have tried:
public static void findClientId(String partnerId, MyClient[] allMyClients) {
Stream.of(allMyClients)
.map(MyClient::getPartners)
.forEach(Partner::getPartnerId)
.filter(
partner ->partner.id.equals(partnerId)))
.map(MyClient::getId);
}
But it complains Non-static method cannot be referenced from a static context
in the line .forEach(Partner::getPartnerId)
答案1
得分: 2
首先，Stream.forEach 是void类型。在它之后无法调用.filter或任何其他方法。除此之外，.map(MyClient::getPartners) 会使你在流水线中丢失 MyClient 的信息，而你实际上想要的是 MyClient.getId。你需要在每个客户端的合作伙伴列表上使用嵌套流进行过滤。
你的代码应该是：
public static String findClientId(String partnerId, MyClient[] allMyClients) {
return Stream.of(allMyClients)
.filter(client -> client.getPartners()
.stream()
.anyMatch(partner -> partner.getPartnerId().equals(partnerId)))
.map(MyClient::getId)
.findAny()
.orElse(null); // 根据需要更改
}
英文:
First, Stream.forEach is void. You can't invoke .filter or any other method after it. Beside that, .map(MyClient::getPartners) would make you lose MyClient information in the pipeline while it's MyClient.getId that you want. You'd have to use a nested stream to for filtering on partner list in each client.
Your code should be:
public static String findClientId(String partnerId, MyClient[] allMyClients) {
return Stream.of(allMyClients)
.filter(client -> client.getPartners()
.stream()
.anyMatch(partner -> partner.getPartnerId().equals(partnerId)))
.map(MyClient::getId)
.findAny()
.orElse(null); // change to whatever is desired
}
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