Spring控制器無法決議從HttpClient發送的JSON（無法構造`java.util.LinkedHashMap`的實體）

我正在嘗試將 JSON 物件發送到 Spring 控制器，控制器將請求正文作為 aMap<String, Object>接收，JSON 本身是正確的，并且通過郵遞員發送相同的 JSON 也可以正常作業，只是當我使用 HttpClient 發送它時。

這是我要發送的 JSON：

{"fruit": "Apple", "color": "Red"}

我的 HTTP 請求：

ObjectMapper mapper = new ObjectMapper();
mapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
String jsonString = mapper.writeValueAsString(body);

HttpRequest request = HttpRequest.newBuilder()
    .uri(new URI(url))
    .header("content-type", "application/json")
    .POST(BodyPublishers.ofString(jsonString))
    .build();
HttpResponse<String> response = client.send(request, BodyHandlers.ofString());

我的控制器：

@PostMapping(value = "/config/addDocument", consumes = {"application/json"})
public void addDocument(@RequestBody Map<String, Object> document)

我收到此錯誤：

HttpMessageNotReadableException: JSON parse error: Cannot construct instance of `java.util.LinkedHashMap` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('{"fruit": "Apple", "color": "Red"}'); nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `java.util.LinkedHashMap` (although at least one Creator exists): no String-argument constructor/factory method to deserialize from String value ('{"fruit": "Apple", "color": "Red"}')<EOL> at [Source: (org.springframework.util.StreamUtils$NonClosingInputStream); line: 1, column: 1]]

我嘗試使用郵遞員發送相同的請求并且它作業正常，創建一個變數字串并發送它也可以正常作業，我在請求方面做錯了什么？

編輯

客戶端來自java.net.http.HttpClient包。

我使用創建了客戶端HttpClient.newHttpClient()

我正在使用 Spring Boot Starter Web 2.7.5。

編輯 2

根據答案，我嘗試將輸入 JSON 字串切換為地圖，并將地圖轉換回 JSON 字串并發送，這樣就可以了。

      ObjectMapper mapper = new ObjectMapper();
      Map<String, Object> map = mapper.readValue(body, Map.class);
      String jsonString = mapper.writeValueAsString(map);

      HttpRequest request = HttpRequest.newBuilder()
          .uri(new URI(url))
          .header("content-type", "application/json")
          .POST(HttpRequest.BodyPublishers.ofString(jsonString))
          .build();
      HttpResponse<String> response = client.send(request, BodyHandlers.ofString());

uj5u.com熱心網友回復：

我使用 Spring Boot 2.7.5、Java 17 嘗試了以下代碼。發送請求的驅動程式代碼。

Map<String, String> body = new LinkedHashMap<>(); //new HashMap() is also fine here
body.put("fruit", "Apple");
body.put("color", "Red");
//Map.of("fruit", "Apple", "color", "Red");
ObjectMapper mapper = new ObjectMapper();
mapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false);
String jsonString = mapper.writeValueAsString(body);

HttpClient client = HttpClient.newHttpClient();

HttpRequest request = HttpRequest.newBuilder()
                     .uri(new URI("http://localhost:8080/test"))
                     .header("content-type", "application/json")
                     .POST(HttpRequest.BodyPublishers.ofString(jsonString))
                     .build();
HttpResponse<String> response = client.send(request, 
                                     HttpResponse.BodyHandlers.ofString());
System.out.println("Status Code : "   response.statusCode());
System.out.println("Headers : "    response.headers());

其余控制器與您在問題中提到的相同。如果我仍然使用它來實體化地圖，Map.of()它作業正常。最后一個 sysout 陳述句輸出到控制臺，如下所示。

標籤：json春天弹簧靴http杰克逊

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