用于从消息负载中提取字段的java spring集成spel表达式

Question

无法通过SPEL获取消息有效载荷。我想从我的消息有效负载的某些字段中提取数据，它本质上是以下JSON转换为Map<String, Object>并传递给@Transformer

{
  "expand":"renderedFields,names,schema,transitions,operations,editmeta,changelog,versionedRepresentations",
  "id":"14730",
  "self":"https://jira.foo.com/rest/api/2/issue/14730",
  "key":"SDP-145",
  "fields":{
    "issuetype":{
      "self":"https://jira.foo.com/rest/api/2/issuetype/10200",
      "id":"10200",
      "description":"gh.issue.epic.desc",
      "iconUrl":"https://jira.foo.com/ghanghor/viewkaka?size=xsmall&kakaId=10501&kakaType=issuetype",
      "name":"Epic",
      "subtask":false,
      "kakaId":10501
    },
    "priority":{
      "self":"https://jira.foo.com/rest/api/2/priority/3",
      "iconUrl":"https://jira.foo.com/images/icons/priorities/major.svg",
      "name":"Major",
      "id":"3"
    },
    "labels":[
      "Lizzy",
      "kanban",
      "rughani"
    ],
    "updated":"2021-01-21T10:33:38.000+0000",
    "status":{
      "self":"https://jira.foo.com/rest/api/2/status/1",
      "description":"The issue is open and ready for the assignee to start work on it.",
      "iconUrl":"https://jira.foo.com/images/icons/statuses/open.png",
      "name":"Open",
      "id":"1",
      "statusCategory":{
        "self":"https://jira.foo.com/rest/api/2/statuscategory/2",
        "id":2,
        "key":"new",
        "colorName":"blue-gray",
        "name":"To Do"
      }
    },
    "summary":"new epic for Tazzy",
    "creator":{
      "self":"https://jira.foo.com/rest/api/2/user?username=skadmin",
      "name":"skadmin",
      "key":"skadmin",
      "emailAddress":"Lizzy.t@foo.com",
      "displayName":"Lizzy Rughani",
      "active":true,
      "timeZone":"Asia/Kolkata"
    },
    "subtasks":[

    ],
  }
}

我对这里的三个嵌套值感兴趣，我试图通过以下表达式获取它们

issueDataMap = {LinkedHashMap@4867}  size = 3
 "name" -> "#payload['fields']['summary']"
 "description" -> "#payload['description']"
 "text3" -> "#payload['key']"

当表达式被应用时，我得到了这个错误

org.springframework.expression.spel.SpelEvaluationException: EL1012E: Cannot index into a null value

下面是我如何在as参数中获得有效载荷的方法

@Transformer
public Map<String, Object> generateCardData(Map<String, Object> payload,
                                            @Header("X-UPSTREAM-WEBHOOK-SOURCE") String projectId) {

接着是

StandardEvaluationContext evaluationContext = evaluationContextFactory.getObject();

下面是我对它的评价

new SpelExpressionParser().parseExpression(issueDataMap.get(key)).getValue(
                            evaluationContext, payload, String.class)));

我用@SpringBootApplication和@EnableInegration注释了应用程序，并自动连接了IntegrationEvaluationContextFactoryBean的一个实例，以获得StandardEvaluationContext

我也试过这个变种

issueDataMap = {LinkedHashMap@4867}  size = 3
 "name" -> "payload['fields']['summary']"
 "description" -> "payload['description']"
 "text3" -> "payload['key']"

但后来我

EL1008E: Property or field 'payload' cannot be found on object of type 'java.util.LinkedHashMap' - maybe not public or not valid?

Answer 1

首先，我们不清楚，当您拥有对对象的完全访问权限时，为什么要在代码中手动使用SpEL。另外，您应该记住，创建StandardEvaluationContext、解析表达式并在每次调用时对其求值，在性能上都是一种开销。您可能只需要更改generateCardData()签名来接受表达式的结果，而不是整个映射。请参阅@Payload.expression属性

无论如何，这不是你想听到的关于你的问题。就在这里： getValue(evaluationContext, payload, String.class)))。根计算对象是payload-a Map。所以，您只需要在表达式定义中假设您可以访问该根对象。因此表达式必须是这样的：fields.summary，description，key

您通常会在文档和示例中看到payload（或header）作为表达式中的第一个标记。这只是因为Spring集成使用Message作为表达式求值的根对象

至于表现。即使在运行时（issueDataMap.get(key)）使用某个键选择表达式的逻辑，您仍然只能对其进行一次解析