HTTPClient Example - Thread “main” java.lang.NoSuchFieldError： INSTANCE 中的 Exception

java apache-httpclient-4.x

2022-09-03 00:53:02

我正在使用Apache的HttpClient组件进行以下简单程序，我看到以下异常：

Exception in thread "main" java.lang.NoSuchFieldError: INSTANCE
    at org.apache.http.impl.io.DefaultHttpRequestWriterFactory.(DefaultHttpRequestWriterFactory.java:52)
    at org.apache.http.impl.io.DefaultHttpRequestWriterFactory.(DefaultHttpRequestWriterFactory.java:56)
    at org.apache.http.impl.io.DefaultHttpRequestWriterFactory.(DefaultHttpRequestWriterFactory.java:46)
    at org.apache.http.impl.conn.ManagedHttpClientConnectionFactory.(ManagedHttpClientConnectionFactory.java:72)
    at org.apache.http.impl.conn.ManagedHttpClientConnectionFactory.(ManagedHttpClientConnectionFactory.java:84)
    at org.apache.http.impl.conn.ManagedHttpClientConnectionFactory.(ManagedHttpClientConnectionFactory.java:59)
    at org.apache.http.impl.conn.PoolingHttpClientConnectionManager$InternalConnectionFactory.(PoolingHttpClientConnectionManager.java:487)
    at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.(PoolingHttpClientConnectionManager.java:147)
    at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.(PoolingHttpClientConnectionManager.java:136)
    at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.(PoolingHttpClientConnectionManager.java:112)
    at org.apache.http.impl.client.HttpClientBuilder.build(HttpClientBuilder.java:726)
    at com.starwood.rms.controller.property.HttpExample.main(HttpExample.java:14)

public class HttpExample {

    public static void main(String[] args) {
        HttpClient client = HttpClientBuilder.create().build();
        HttpGet request = new HttpGet("https://www.google.com/?q=java");

        try {
            HttpResponse response = client.execute(request);
            System.out.println(response.getStatusLine());

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

我正在使用

Httpclient-4.3.3.jar
httpcore-4.3.2.jar

有什么想法吗？

答案 1

我在Hadoop上遇到了这个问题。它使用了旧版本的和在他们的共享库中。httpclient-4.2.5.jarhttpcore-4.2.5.jar

我通过maven-shade-plugin对部分进行着色来解决这个问题

<relocations>
    <relocation>
        <pattern>org.apache.http</pattern>
        <shadedPattern>shaded.org.apache.http</shadedPattern>
    </relocation>
</relocations>

答案 2

查看DefaultHttpRequestWriterFactory的源代码

package org.apache.http.impl.io;

import org.apache.http.HttpRequest;
import org.apache.http.annotation.Immutable;
import org.apache.http.io.HttpMessageWriter;
import org.apache.http.io.HttpMessageWriterFactory;
import org.apache.http.io.SessionOutputBuffer;
import org.apache.http.message.BasicLineFormatter;
import org.apache.http.message.LineFormatter;

@Immutable

public class  [More ...] DefaultHttpRequestWriterFactory implements HttpMessageWriterFactory<HttpRequest> {

    public static final DefaultHttpRequestWriterFactory INSTANCE = new DefaultHttpRequestWriterFactory();

    private final LineFormatter lineFormatter;

    public  [More ...] DefaultHttpRequestWriterFactory(final LineFormatter lineFormatter) {
        super();
        this.lineFormatter = lineFormatter != null ? lineFormatter : BasicLineFormatter.INSTANCE;
    }

    public  [More ...] DefaultHttpRequestWriterFactory() {
        this(null);
    }

    public HttpMessageWriter<HttpRequest>  [More ...] create(final SessionOutputBuffer buffer) {
        return new DefaultHttpRequestWriter(buffer, lineFormatter);
    }

}

您确定您使用的是 HttpCore 4.3.2 吗？尝试解决DefaultHttpRequestWriterFactory

BasicLineFormatter.INSTANCE

字段，但找不到它。

检查您的类路径中是否有可能包含另一个类的库，也许您有一个与4.3.2版本冲突的旧版本的HttpCore。BasicLineFormatter