Java Http客户端-无此类字段错误

Question

I am trying to use the Digital Ocean java library and when trying to create a connection with:

CloseableHttpClient httpClient = HttpClients.createDefault();

client = new DigitalOceanClient("v2", token, httpClient);

The problem lies in the CloseableHttpClient httpClient object. The library uses httpcore version 4.4.1 and httpclient version 4.5. It gives me a java.lang.NoSuchFieldError.

Here's my log:

Exception in thread "main" java.lang.NoSuchFieldError: INSTANCE
at org.apache.http.conn.ssl.SSLConnectionSocketFactory.<clinit>(SSLConnectionSocketFactory.java:144)
at org.apache.http.impl.client.HttpClientBuilder.build(HttpClientBuilder.java:955)
at org.apache.http.impl.client.HttpClients.createDefault(HttpClients.java:58)
at main.java.servers.DigitalOceanServer.setup(DigitalOceanServer.java:28)

I found little information and documentation on the NoSuchFieldError, so I'm assuming it has to do with the version of httpcore and/or httpclient that causes this error.

Answer 1

The field variable INSTANCE has been introduced in AllowAllHostnameVerifier.java since Apache httpclient version 4.4.

• AllowAllHostnameVerifier of version 4.3.6
• AllowAllHostnameVerifier of version 4.4.0
• SSLConnectionSocketFactory of version 4.3.6
• SSLConnectionSocketFactory of version 4.4.0

If both new version of SSLConnectionSocketFactory and old version of AllowAllHostnameVerifier is used, then java.lang.NoSuchFieldError: INSTANCE is thrown.

One of the possible cause is two version of Apache httpclient jar are in your library directory.