{"id":9193,"date":"2022-02-23T22:30:36","date_gmt":"2022-02-23T22:30:36","guid":{"rendered":"http:\/\/putridparrot.com\/blog\/?p=9193"},"modified":"2022-02-23T22:36:25","modified_gmt":"2022-02-23T22:36:25","slug":"interacting-with-eureka-from-swift-5","status":"publish","type":"post","link":"https:\/\/putridparrot.com\/blog\/interacting-with-eureka-from-swift-5\/","title":{"rendered":"Interacting with Eureka from Swift 5"},"content":{"rendered":"

I wanted to get my little Swift console application (developed in the post Creating a console app. in Swift (on Linux)<\/a>) working with Eureka. <\/p>\n

So in the last post I outlined the simple steps to get Eureka up and running in docker<\/a>. Now let’s combine these posts along with the information from my the post Interacting with Eureka via it\u2019s REST operations<\/a> and create ourselves a Swift Eureka client.<\/p>\n

Before I get started, I have not found the generation of JSON from types or for that matter generating the Dictionary required for JSONSerialization as intuitive as C# (for example). I’m not sure if there’s a better way to do these things, but this code works so it’ll do for now. But if you know a better way please use it.<\/em><\/p>\n

To start with we’re just going to manually generate our JSON string to match the POST request that we need to tell EUREKA that our application is starting<\/p>\n

\r\nlet json: String = "{" +\r\n  "\\"instance\\": {" +\r\n    "\\"hostName\\": \\"myhost\\"," +\r\n    "\\"app\\": \\"SWIFT-EUREKA\\"," +\r\n    "\\"vipAddress\\": \\"myservice\\"," +\r\n    "\\"secureVipAddress\\": \\"myservice\\"," +\r\n    "\\"ipAddr\\": \\"10.0.0.10\\"," +\r\n    "\\"status\\": \\"STARTING\\"," +\r\n    "\\"port\\": {\\"$\\": \\"8080\\", \\"@enabled\\": \\"true\\"}," +\r\n    "\\"securePort\\": {\\"$\\": \\"8443\\", \\"@enabled\\": \\"true\\"}," +\r\n    "\\"healthCheckUrl\\": \\"http:\/\/myservice:8080\/healthcheck\\"," +\r\n    "\\"statusPageUrl\\": \\"http:\/\/myservice:8080\/status\\"," +\r\n    "\\"homePageUrl\\": \\"http:\/\/myservice:8080\\"," +\r\n    "\\"dataCenterInfo\\": {" +\r\n      "\\"@class\\": \\"com.netflix.appinfo.InstanceInfo$DefaultDataCenterInfo\\", " +\r\n      "\\"name\\": \\"MyOwn\\"" +\r\n    "}" +\r\n  "}" +\r\n"}"\r\n<\/pre>\n
Hopefully this is fairly obvious (even with all the escaping characters) what we’re doing, but to use this in JSONSerialization.data method is seems we need to convert this string to a Dictionary or Array, so here’s an extension method to convert to a dictionary<\/p>\n
\r\nextension String {\r\n  func toDictionary() -> [String:AnyObject]? {\r\n    if let data = self.data(using: .utf8) {\r\n      return try? JSONSerialization.jsonObject(with: data, options: .mutableContainers) as? [String:AnyObject]\r\n    }\r\n    return nil\r\n  } \r\n}\r\n<\/pre>\n
There’s zero error handling here – I leave it to the reader to add that.<\/em><\/p>\n
So using the extension method toDictionary<\/em> we’ll convert our JSON string into a dictionary which is then passed into the JSONSerialization.data to create a Data object, i.e.<\/p>\n
\r\nlet data = json.toDictionary()\r\nlet httpBody = try JSONSerialization.data(withJSONObject: data!, options: [])\r\n<\/pre>\n
Now we’ll create the URL and URLRequest to call the Eureka service<\/p>\n
\r\nlet url = URL(string: "http:\/\/192.168.1.1:8761\/eureka\/apps\/swift-eureka")\r\nvar request = URLRequest(url: url!)\r\nrequest.httpMethod = "POST"\r\nrequest.setValue("application\/json", forHTTPHeaderField: "Content-Type")\r\nrequest.setValue("application\/json", forHTTPHeaderField: "Accept")\r\nrequest.httpBody = httpBody\r\nrequest.timeoutInterval = 20\r\n<\/pre>\n
The rest of the code is the same as Creating a console app. in Swift (on Linux)<\/a> but for completeness it’s list below in it’s entirety (don’t forget the extension method toDictionary is in some extension file).<\/p>\n
\r\nimport Foundation\r\n#if canImport(FoundationNetworking)\r\nimport FoundationNetworking\r\n#endif\r\n\r\nlet session = URLSession.shared\r\nlet semaphore = DispatchSemaphore(value: 0)\r\n\r\nlet json: String = "{" +\r\n  "\\"instance\\": {" +\r\n    "\\"hostName\\": \\"myhost\\"," +\r\n    "\\"app\\": \\"SWIFT-EUREKA\\"," +\r\n    "\\"vipAddress\\": \\"myservice\\"," +\r\n    "\\"secureVipAddress\\": \\"myservice\\"," +\r\n    "\\"ipAddr\\": \\"10.0.0.10\\"," +\r\n    "\\"status\\": \\"DOWN\\"," +\r\n    "\\"port\\": {\\"$\\": \\"8080\\", \\"@enabled\\": \\"true\\"}," +\r\n    "\\"securePort\\": {\\"$\\": \\"8443\\", \\"@enabled\\": \\"true\\"}," +\r\n    "\\"healthCheckUrl\\": \\"http:\/\/myservice:8080\/healthcheck\\"," +\r\n    "\\"statusPageUrl\\": \\"http:\/\/myservice:8080\/status\\"," +\r\n    "\\"homePageUrl\\": \\"http:\/\/myservice:8080\\"," +\r\n    "\\"dataCenterInfo\\": {" +\r\n      "\\"@class\\": \\"com.netflix.appinfo.InstanceInfo$DefaultDataCenterInfo\\", " +\r\n      "\\"name\\": \\"MyOwn\\"" +\r\n    "}" +\r\n  "}" +\r\n"}"\r\n\r\nlet data = json.toDictionary()\r\nlet httpBody = try? JSONSerialization.data(withJSONObject: data!, options: [])\r\n\r\nlet url = URL(string: "http:\/\/192.168.0.88:8761\/eureka\/apps\/swift-eureka")\r\nvar request = URLRequest(url: url!)\r\nrequest.httpMethod = "POST"\r\nrequest.setValue("application\/json", forHTTPHeaderField: "Content-Type")\r\nrequest.setValue("application\/json", forHTTPHeaderField: "Accept")\r\nrequest.httpBody = httpBody\r\nrequest.timeoutInterval = 20\r\n\r\nsession.dataTask(with: request) { (data, response, error) in\r\n    let result = String.init(data: data!, encoding: .utf8)\r\n    print(result!)\r\n    semaphore.signal()\r\n}.resume()\r\n\r\nsemaphore.wait()\r\n<\/pre>\n
At this time I haven’t got a great solution for using types to define our request as the request has some invalid name keys, such as $ and @enabled (again there may be a solution which I’ve not come across yet). To give the reader a starting point, here’s the code I have for turning my EurekaRequest type into a JSON string. <\/p>\n
I’ve not included the EurekaRequest so this really just shows a way to convert a type to a JSON string.<\/em><\/p>\n
\r\nlet instance = EurekaRequest()\r\nlet encoder = JSONEncoder();\r\n\/\/ required to stop \/\/ becoming \\\/\r\nencoder.outputFormatting = .withoutEscapingSlashes\r\nlet jsonData = try encoder.encode(instance)\r\n\r\n\/\/ convert to a string\r\nvar json = String(data: jsonData, encoding: String.Encoding.utf8)!;\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"
I wanted to get my little Swift console application (developed in the post Creating a console app. in Swift (on Linux)) working with Eureka. So in the last post I outlined the simple steps to get Eureka up and running in docker. Now let’s combine these posts along with the information from my the post […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[240,286],"tags":[],"class_list":["post-9193","post","type-post","status-publish","format-standard","hentry","category-eureka","category-swift"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/posts\/9193","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/comments?post=9193"}],"version-history":[{"count":5,"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/posts\/9193\/revisions"}],"predecessor-version":[{"id":9201,"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/posts\/9193\/revisions\/9201"}],"wp:attachment":[{"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/media?parent=9193"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/categories?post=9193"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/putridparrot.com\/blog\/wp-json\/wp\/v2\/tags?post=9193"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}