Question

我正在尝试使用HTTPClient编写一个简单的WebService测试。我已经装满了所有的罐子，但得到了上面的错误信息。

为什么我收到此错误消息？

以下是代码：

package HTTPClientTest;

import java.io.IOException;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpUriRequest;
import org.apache.http.impl.client.HttpClientBuilder;
import org.junit.Assert;


public class RESTTester {

    public static void main (String args[]) {

    String restURL_XML = "http://parabank.parasoft.com/parabank/services/bank/customers/12212/";


    try {

    testStatusCode(restURL_XML);

    } catch (ClientProtocolException e) {

    e.printStackTrace();
    } catch (IOException e) {
    e.printStackTrace();
    } 
}


public static void testStatusCode(String restURL) throws ClientProtocolException, IOException {
    HttpUriRequest request = new HttpGet(restURL);
    HttpResponse httpResponse = HttpClientBuilder.create().build().execute(request);
    Assert.assertEquals(httpResponse.getStatusLine().getStatusCode(),HttpStatus.SC_OK);
    }

}

下面是错误堆栈跟踪，

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:966)
    at HTTPClientTest.RESTTester.testStatusCode(RESTTester.java:37)
    at HTTPClientTest.RESTTester.main(RESTTester.java:22)

Answer 1

我遇到了上述错误，因为我的项目中有多个旧版本的HTTPClient。我删除了旧版本的HTTPClient，现在错误信息消失了。

Answer 2

通过分析您的堆栈跟踪，我发现您的程序写得很好。似乎apache HTTP API编译错误。也许包org.apache.http.impl.client是根据您使用的org.apache.http.conn.ssl的不同版本编译的？将两个软件包升级到最新版本并重试。将其报告给HTTPClient bug跟踪器。

Answer 3

我ve come across this error(java.lang.NoSuchFieldError: INSTANCE) several times. With different reasons here it is INSTANCE. This error is conveying about the mismatch between the aws-java-sdk-core library and one of the service-specific SDK的aws-sdk-s3或aws-java-sdk-sqs。

我在将aws-java-sdk-core（1.11.289）与aws-sdk-s3（1.11.428）结合使用时遇到此错误。通过将以下aws-java-sdk-core（1.11.289）与aws-sdk-s3（1.11.186）一起进行修复。

线程＆＃34; main＆＃34;中的例外情况java.lang.NoSuchFieldError：INSTANCE

3 个答案: