Schema 教程第22课：连接服务时处理错误
第22课：连接服务时处理错误
从外部 API 获取数据时，可能会遇到各种类型的错误。
例如，请考虑以下 query：
{
externalData: _sendJSONObjectItemHTTPRequest(
input: {
url: "https://newapi.getpop.org/wp-json/wp/v2/posts/8888/"
}
)
postTitle: _objectProperty(
object: $__externalData,
by: { path: "title.rendered"}
)
}如果网络连接断开，则字段 _sendJSONObjectItemHTTPRequest 将触发错误：
{
"errors": [
{
"message": "cURL error 6: Could not resolve host: newapi.getpop.org (see https://curl.haxx.se/libcurl/c/libcurl-errors.html) for https://newapi.getpop.org/wp-json/wp/v2/posts/8888/",
"locations": [
{
"line": 2,
"column": 17
}
],
"extensions": {
"path": [
"externalData: _sendJSONObjectItemHTTPRequest(input: {url: \"https://newapi.getpop.org/wp-json/wp/v2/posts/8888/\"}) @export(as: \"externalData\")",
"query { ... }"
],
"type": "QueryRoot",
"field": "externalData: _sendJSONObjectItemHTTPRequest(input: {url: \"https://newapi.getpop.org/wp-json/wp/v2/posts/8888/\"}) @export(as: \"externalData\")",
"id": "root",
"code": "PoP/ComponentModel@e1"
}
},
{
"message": "Argument 'object' in field '_objectProperty' of type 'QueryRoot' cannot be null",
"locations": [
{
"line": 10,
"column": 13
}
],
"extensions": {
"path": [
"$__externalData",
"(object: $__externalData)",
"postTitle: _objectProperty(object: $__externalData, by: {path: \"title.rendered\"})",
"query { ... }"
],
"type": "QueryRoot",
"field": "postTitle: _objectProperty(object: $__externalData, by: {path: \"title.rendered\"})",
"id": "root",
"code": "gql@5.4.2.1[b]",
"specifiedBy": "https://spec.graphql.org/draft/#sec-Required-Arguments"
}
}
],
"data": {
"externalData": null,
"postTitle": null
}
}如果连接成功，但请求的资源不存在，则会收到 404：
{
"errors": [
{
"message": "Client error: `GET https://newapi.getpop.org/wp-json/wp/v2/posts/8888/` resulted in a `404 Not Found` response:\n{\"code\":\"rest_post_invalid_id\",\"message\":\"Invalid post ID.\",\"data\":{\"status\":404}}\n",
"locations": [
{
"line": 2,
"column": 17
}
],
"extensions": {
"path": [
"externalData: _sendJSONObjectItemHTTPRequest(input: {url: \"https://newapi.getpop.org/wp-json/wp/v2/posts/8888/\"}) @export(as: \"externalData\")",
"query { ... }"
],
"type": "QueryRoot",
"field": "externalData: _sendJSONObjectItemHTTPRequest(input: {url: \"https://newapi.getpop.org/wp-json/wp/v2/posts/8888/\"}) @export(as: \"externalData\")",
"id": "root",
"code": "PoP/ComponentModel@e1"
}
},
{
"message": "Argument 'object' in field '_objectProperty' of type 'QueryRoot' cannot be null",
"locations": [
{
"line": 10,
"column": 13
}
],
"extensions": {
"path": [
"$__externalData",
"(object: $__externalData)",
"postTitle: _objectProperty(object: $__externalData, by: {path: \"title.rendered\"})",
"query { ... }"
],
"type": "QueryRoot",
"field": "postTitle: _objectProperty(object: $__externalData, by: {path: \"title.rendered\"})",
"id": "root",
"code": "gql@5.4.2.1[b]",
"specifiedBy": "https://spec.graphql.org/draft/#sec-Required-Arguments"
}
}
],
"data": {
"externalData": null,
"postTitle": null
}
}在两种情况下，响应中都出现了额外的错误：
{
"message": "Argument 'object' in field '_objectProperty' of type 'QueryRoot' cannot be null"
}出现此错误的原因是，第一个错误发生后，动态变量 $__externalData 的值变为 null，从而触发了第二个错误。这并不理想；我们更希望在发现某个错误后，跳过剩余 GraphQL query 的执行。
在本教程课程中，我们将探讨如何实现这一目标。
连接 REST API 时处理错误
此 GraphQL query 将逻辑拆分为两个操作，其中：
- 第一个操作导出动态变量
$requestProducedErrors，指示字段_sendJSONObjectItemHTTPRequest的值是否为null（若如此，则表示发生了某个错误） - 当
$requestProducedErrors为true时，第二个操作将被@skip
这样，包含要执行逻辑的第二个操作，在第一个操作获取数据时出错的情况下将被跳过：
query ConnectToRESTEndpoint($postId: ID!) {
endpoint: _sprintf(
string: "https://newapi.getpop.org/wp-json/wp/v2/posts/%s/?_fields=id,type,title,date"
values: [$postId]
) @remove
externalData: _sendJSONObjectItemHTTPRequest(
input: {
url: $__endpoint
}
) @export(as: "externalData")
requestProducedErrors: _isNull(value: $__externalData)
@export(as: "requestProducedErrors")
@remove
}
query ExecuteOperation
@depends(on: "ConnectToRESTEndpoint")
@skip(if: $requestProducedErrors)
{
# Do something...
postTitle: _objectProperty(
object: $externalData,
by: { path: "title.rendered"}
)
}传入 $postId: 1 时，query 成功执行，响应如下：
{
"data": {
"externalData": {
"id": 1,
"date": "2019-08-02T07:53:57",
"type": "post",
"title": {
"rendered": "Hello world!"
}
},
"postTitle": "Hello world!"
}
}传入 $postId: 8888 查询不存在的资源时，会得到以下响应（注意响应中没有 postTitle，也没有第二条错误信息）：
{
"errors": [
{
"message": "Client error: `GET https://newapi.getpop.org/wp-json/wp/v2/posts/8888/?_fields=id,type,title,date` resulted in a `404 Not Found` response:\n{\"code\":\"rest_post_invalid_id\",\"message\":\"Invalid post ID.\",\"data\":{\"status\":404}}\n",
"locations": [
{
"line": 6,
"column": 17
}
],
"extensions": {
"path": [
"externalData: _sendJSONObjectItemHTTPRequest(input: {url: $__endpoint}) @export(as: \"externalData\")",
"query ConnectToRESTEndpoint($postId: ID!) { ... }"
],
"type": "QueryRoot",
"field": "externalData: _sendJSONObjectItemHTTPRequest(input: {url: $__endpoint}) @export(as: \"externalData\")",
"id": "root",
"code": "PoP/ComponentModel@e1"
}
}
],
"data": {
"externalData": null
}
}如果网络连接断开，则会得到以下响应：
{
"errors": [
{
"message": "cURL error 6: Could not resolve host: newapi.getpop.org (see https://curl.haxx.se/libcurl/c/libcurl-errors.html) for https://newapi.getpop.org/wp-json/wp/v2/posts/8888/?_fields=id,type,title,date",
"locations": [
{
"line": 17,
"column": 17
}
],
"extensions": {
"path": [
"externalData: _sendHTTPRequest(input: {url: $__endpoint, method: GET}) { ... }",
"query ConnectToAPI($postId: ID!) @depends(on: \"ExportDefaultDynamicVariables\") { ... }"
],
"type": "QueryRoot",
"field": "externalData: _sendHTTPRequest(input: {url: $__endpoint, method: GET}) { ... }",
"id": "root",
"code": "PoP/ComponentModel@e1"
}
}
],
"data": {
"externalData": null
}
}显示 REST API 响应中的错误信息
上一个 query 使用了字段 _sendJSONObjectItemHTTPRequest，该字段期望状态码为 200（或其他成功码）。
然而，REST API 有可能对不存在的资源返回 404，并在 JSON 响应中提供描述性错误信息。
通过将 _sendJSONObjectItemHTTPRequest 替换为 _sendHTTPRequest，可以捕获来自 Web 服务器的这些反馈，并在 GraphQL 响应的 errors 条目中显示。
例如，从 WP REST API 获取不存在的资源数据时，响应中会返回 data.status 条目及相关数据。
此 GraphQL query 捕获这些数据，并通过使用 Response Error Trigger 扩展提供的字段 _fail，显式添加包含响应错误代码和信息的错误条目：
query ExportDefaultDynamicVariables
@configureWarningsOnExportingDuplicateVariable(enabled: false)
{
defaultEndpointHasErrors: _echo(value: true)
@export(as: "endpointHasErrors")
@remove
}
query ConnectToAPI($postId: ID!)
@depends(on: "ExportDefaultDynamicVariables")
{
endpoint: _sprintf(
string: "https://newapi.getpop.org/wp-json/wp/v2/posts/%s/?_fields=id,type,title,date"
values: [$postId]
) @remove
externalData: _sendHTTPRequest(
input: {
url: $__endpoint,
method: GET
}
) {
contentType
statusCode
body @remove
bodyJSONObject: _strDecodeJSONObject(string: $__body)
@export(as: "externalData")
}
isNullExternalData: _isNull(value: $__externalData)
@export(as: "isNullExternalData")
@remove
}
query ValidateAPIResponse
@depends(on: "ConnectToAPI")
@skip(if: $isNullExternalData)
{
endpointHasErrors: _propertyIsSetInJSONObject(
object: $externalData
by: {
path: "data.status"
}
)
@export(as: "endpointHasErrors")
@remove
}
query FailIfExternalAPIHasErrors($postId: ID!)
@depends(on: "ValidateAPIResponse")
@include(if: $endpointHasErrors)
@skip(if: $isNullExternalData)
{
code: _objectProperty(
object: $externalData,
by: {
key: "code"
}
) @remove
message: _objectProperty(
object: $externalData,
by: {
key: "message"
}
) @remove
errorMessage: _sprintf(
string: "[%s] %s",
values: [$__code, $__message]
) @remove
data: _objectProperty(
object: $externalData,
by: {
key: "data"
}
) @remove
_fail(
message: $__errorMessage
data: {
postId: $postId,
endpointData: $__data
}
) @remove
}
query ExecuteSomeOperation
@depends(on: "FailIfExternalAPIHasErrors")
@skip(if: $endpointHasErrors)
{
# Do something...
postTitle: _objectProperty(
object: $externalData,
by: { path: "title.rendered"}
)
}Response Error Trigger 扩展提供了两种在 errors 下添加自定义条目的方式：
- 通过字段
_fail - 通过指令
@fail
字段 _fail 始终添加错误，而指令 @fail 仅在参数 condition 的条件满足时才添加。其默认值为 IS_NULL，意味着当应用该指令的字段值为 null 时将被触发：
query GetPost($id: ID!) {
post(by:{id: $id})
@fail(
message: "There is no post with the provided ID"
data: {
id: $id
}
)
{
id
title
}
}使用变量 $postId: 1 执行 query 时，请求成功，得到以下结果：
{
"data": {
"externalData": {
"contentType": "application/json; charset=UTF-8",
"statusCode": 200,
"bodyJSONObject": {
"id": 1,
"date": "2019-08-02T07:53:57",
"type": "post",
"title": {
"rendered": "Hello world!"
}
}
},
"postTitle": "Hello world!"
}
}使用变量 $postId: 8888 执行 query 时，资源不存在，得到以下结果：
{
"errors": [
{
"message": "[rest_post_invalid_id] Invalid post ID.",
"locations": [
{
"line": 76,
"column": 3
}
],
"extensions": {
"path": [
"_fail(message: $__errorMessage, data: {postId: $postId, endpointData: $__data}) @remove",
"query FailIfExternalAPIHasErrors($postId: ID!) @depends(on: \"ValidateAPIResponse\") @include(if: $endpointHasErrors) @skip(if: $isNullExternalData) { ... }"
],
"type": "QueryRoot",
"field": "_fail(message: $__errorMessage, data: {postId: $postId, endpointData: $__data}) @remove",
"id": "root",
"failureData": {
"postId": 8888,
"endpointData": {
"status": 404
}
},
"code": "PoPSchema/FailFieldAndDirective@e1"
}
}
],
"data": {
"externalData": {
"contentType": "application/json; charset=UTF-8",
"statusCode": 404,
"bodyJSONObject": {
"code": "rest_post_invalid_id",
"message": "Invalid post ID.",
"data": {
"status": 404
}
}
}
}
}连接 GraphQL API 时处理错误
在 GraphQL API 中查询不存在的资源时，响应状态码将为 200，该资源的值为 null（这与 REST 不同，REST 会返回 404）。
以下 GraphQL query 通过检查以下条件来验证执行 _sendGraphQLHTTPRequest 时没有发生错误：
- 响应不为
null（例如：网络连接未断开） - 响应不包含
errors条目 - 响应在
data.post条目下包含非null值（即查询的资源存在）
query InitializeDynamicVariables
@configureWarningsOnExportingDuplicateVariable(enabled: false)
{
defaultResponseHasErrors: _echo(value: false)
@export(as: "responseHasErrors")
@remove
defaultPostIsMissing: _echo(value: false)
@export(as: "postIsMissing")
@remove
}
query ConnectToGraphQLAPI($postId: ID!)
@depends(on: "InitializeDynamicVariables")
{
externalData: _sendGraphQLHTTPRequest(
input: {
endpoint: "https://newapi.getpop.org/api/graphql/",
query: """
query GetPostData($postId: ID!) {
post(by: { id : $postId }) {
date
title
}
}
""",
variables: [
{
name: "postId",
value: $postId
}
]
}
) @export(as: "externalData")
requestProducedErrors: _isNull(value: $__externalData)
@export(as: "requestProducedErrors")
@remove
}
query ValidateResponse
@depends(on: "ConnectToGraphQLAPI")
@skip(if: $requestProducedErrors)
{
responseHasErrors: _propertyIsSetInJSONObject(
object: $externalData
by: {
key: "errors"
}
)
@export(as: "responseHasErrors")
@remove
postExists: _propertyIsSetInJSONObject(
object: $externalData
by: {
path: "data.post"
}
)
@remove
postIsMissing: _not(value: $__postExists)
@export(as: "postIsMissing")
@remove
}
query FailIfResponseHasErrors
@depends(on: "ValidateResponse")
@skip(if: $requestProducedErrors)
@skip(if: $postIsMissing)
@include(if: $responseHasErrors)
{
errors: _objectProperty(
object: $externalData,
by: {
key: "errors"
}
) @remove
_fail(
message: "Executing the GraphQL query produced error(s)"
data: {
errors: $__errors
}
) @remove
}
query ExecuteOperation
@depends(on: "FailIfResponseHasErrors")
@skip(if: $requestProducedErrors)
@skip(if: $responseHasErrors)
@skip(if: $postIsMissing)
{
# Do something...
postTitle: _objectProperty(
object: $externalData,
by: { path: "data.post.title" }
)
}传入 $postId: 1 时，query 成功执行，响应如下：
{
"data": {
"externalData": {
"data": {
"post": {
"date": "2019-08-02T07:53:57+00:00",
"title": "Hello world!"
}
}
},
"postTitle": "Hello world!"
}
}传入 $postId: 8888 查询不存在的资源时，会得到以下响应（注意响应中没有 postTitle，也没有错误信息）：
{
"data": {
"externalData": {
"data": {
"post": null
}
}
}
}如果网络连接断开，则会得到以下响应：
{
"errors": [
{
"message": "cURL error 6: Could not resolve host: newapi.getpop.org (see https://curl.haxx.se/libcurl/c/libcurl-errors.html) for https://newapi.getpop.org/api/graphql/",
"locations": [
{
"line": 15,
"column": 17
}
],
"extensions": {
"path": [
"externalData: _sendGraphQLHTTPRequest(input: {endpoint: \"https://newapi.getpop.org/api/graphql/\", query: \"\n query GetPostData($postId: ID!) {\n post(by: { id : $postId }) {\n date\n title\n }\n }\n \", variables: [{name: \"postId\", value: $postId}]}) @export(as: \"externalData\")",
"query ConnectToGraphQLAPI($postId: ID!) @depends(on: \"InitializeDynamicVariables\") { ... }"
],
"type": "QueryRoot",
"field": "externalData: _sendGraphQLHTTPRequest(input: {endpoint: \"https://newapi.getpop.org/api/graphql/\", query: \"\n query GetPostData($postId: ID!) {\n post(by: { id : $postId }) {\n date\n title\n }\n }\n \", variables: [{name: \"postId\", value: $postId}]}) @export(as: \"externalData\")",
"id": "root",
"code": "PoP/ComponentModel@e1"
}
}
],
"data": {
"externalData": null
}
}在请求的资源不存在时产生错误
在上述 GraphQL query 中，如果查询的文章不存在，只会返回 null，errors 下不会有错误条目。
如果希望在这种情况下强制添加错误，可以追加以下操作，使用字段 _fail 来触发错误：
query FailIfPostNotExists($postId: ID!)
@skip(if: $requestProducedErrors)
@include(if: $postIsMissing)
@depends(on: "ValidateResponse")
{
errorMessage: _sprintf(
string: "There is no post with ID '%s'",
values: [$postId]
) @remove
_fail(
message: $__errorMessage
data: {
id: $postId
}
) @remove
}
query ExecuteOperation
@depends(on: [
"FailIfResponseHasErrors",
"FailIfPostNotExists"
])
# ...
{
# ...
}现在，传入 $postId: 8888 查询不存在的资源时，会得到以下响应：
{
"errors": [
{
"message": "There is no post with ID '8888'",
"locations": [
{
"line": 96,
"column": 3
}
],
"extensions": {
"path": [
"_fail(message: $__errorMessage, data: {id: $postId}) @remove",
"query FailIfPostNotExists($postId: ID!) @skip(if: $requestProducedErrors) @include(if: $postIsMissing) @depends(on: \"ValidateResponse\") { ... }"
],
"type": "QueryRoot",
"field": "_fail(message: $__errorMessage, data: {id: $postId}) @remove",
"id": "root",
"failureData": {
"id": 8888
},
"code": "PoPSchema/FailFieldAndDirective@e1"
}
}
],
"data": {
"externalData": {
"data": {
"post": null
}
}
}
}Prev
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