HTTPClient示例 - 线程"main"中的异常java.lang.NoSuchFieldError:INSTANCE

Question

我正在使用Apache的HttpClient组件来完成以下简单程序,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();
        }
    }
}

我在用

• HttpClient的-4.3.3.jar
• 的HttpCore-4.3.2.jar

有任何想法吗？

Answer 1

我有Hadoop这个问题.它使用的旧版本httpclient-4.2.5.jar,并httpcore-4.2.5.jar在他们的共享库.

我通过maven-shade-plugin对部件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>

Answer 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);
    }

}

你确定你使用的是HttpCore 4.3.2吗？DefaultHttpRequestWriterFactory试着解决

BasicLineFormatter.INSTANCE

领域却无法找到它.

检查你的类路径中是否包含可能包含另一个BasicLineFormatter类的库,也许你有旧版本的HttpCore与4.3.2版本冲突.

Answer 3

引起:java.lang.NoSuchFieldError:INSTANCE

java.lang.NoSuchFieldError的解决方案之一:INSTANCE :如果我们的类路径中有两个相同类的diff版本,就会发生这种情况.... [...],所以我们首先找到该类(一个版本的类),单击该类,选择"构建路径",然后单击"从构建路径中删除".由333ccc333

Answer 4

这段代码有效...没有任何错误..如果您使用类似的 import ，请检查包。

package com.jai.http;

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.HttpClientBuilder;

public class HttpExample {

    /**
     * @param args
     */
    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();

        }

    }
}