我有一个静态方法，旨在使用 ObjectMapper 读取 JSON 并解析为类(在运行时指定)。我想返回“N”类型的对象，但我收到有关使用泛型的错误。
如何让下面的代码完成这个任务？
public static <N, T extends AbstractRESTApplication> N GET_PAYLOAD( T app, String urlString, REQUEST_TYPE requestType) throws JsonProcessingException, MalformedURLException, IOException, NoSuchAlgorithmException, KeyManagementException {
HttpsURLConnection con = null;
try {
RSSFeedParser.disableCertificateValidation();
URL url = new URL(urlString);
con = (HttpsURLConnection) url.openConnection();
String encoding = Base64.getEncoder().encodeToString((app.getUser() + ":" + app.getPassword()).getBytes("UTF-8"));
con.setRequestProperty("Authorization", String.format("Basic %s", encoding));
//con.setDoOutput(true);//only used for writing to.
con.setDoInput(true);
con.setRequestProperty("Content-Type", "application/json; charset=UTF-8");
con.setRequestMethod(requestType.toString());
con.setRequestProperty("User-Agent", "Java client");
DataOutputStream wr = new DataOutputStream(con.getOutputStream());
// wr.write(val);
StringBuilder content;
try (BufferedReader in = new BufferedReader(
new InputStreamReader(con.getInputStream()))) {
String line;
content = new StringBuilder();
while ((line = in.readLine()) != null) {
content.append(line);
content.append(System.lineSeparator());
}
System.out.println(Class.class.getName() + ".GET_PAYLOAD= " + content);
//Map Content to Class.
ObjectMapper om = new ObjectMapper();
return om.readValue(content.toString(),N);//Doesn't Like N type. How do i fix?
}
} finally {
con.disconnect();
}
}
最佳答案
Java 泛型是使用“类型删除”来实现的。这意味着编译器可以检查类型安全性并在运行时删除类型。
所以你不能像这样使用你的类型变量(“N”)。您必须将实际的类作为参数传递:
public static <N, T extends AbstractRESTApplication> N GET_PAYLOAD( T app,
String urlString, REQUEST_TYPE requestType,
Class<N> nClass) throws ... {
return om.readValue(content.toString(), nClass);
关于java - Jackson ObjectMapper 中的泛型静态方法，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/62455419/