FileDownload https 自签名证书问题 报错：CertPathValidatorException

一：前言

    项目安全升级，使用https协议，老板不出钱，只能使用自签名证书的方式，发现Filedownload 无法下载文件，报错：

javax.net.ssl.SSLHandshakeException: java.security.cert.CertPathValidatorException: Trust anchor for certification path not found. 大致意思：信任锚认证路径找不到。

二：问题分析

    自签名证书没有经过CA认证，肯定会抛此异常，没办法，谁让用的是自签名的证书呢， 只能先忽略SSL认证，开始找FileDownload忽略SSL验证的相关接口，百度一圈无果，难道没人遇到这样的问题吗？

三：解决方案：

    经过求助作者得到以下答案：

有思路了， 哐哐哐就是一顿干，实现了FileDownloadConnection的接口，写了一个自己的FileDownloadUrlConnection

满心欢喜的验证结果，结果不出意外， 没有生效。是我写的不对? 仔细查看lssues，发现了新大陆

作者自己有实现过FileDownloadUrlConnection， 使用的是okhttp（默认是httpurlconnection），赶紧拿来试试，先下载一个http的链接，叮！！！成功了。赶紧添加忽略SSL的代码，换成https 的链接试试，好的，成功。。

方案总结：

    1. 使用作者实现的OkHttp3Connection替换FileDownload的默认连接方式（httpurlconnection）

    2. 在创建okhttp实例的时候添加忽略SSL验证的代码

    3. 使用FileDownloader.setupOnApplicationOnCreate(this).connectionCreator（....）的方式注册FileDownload

贴上全部源码：

OkHttp3Connection.java(作者实现的)

import com.liulishuo.filedownloader.connection.FileDownloadConnection;
import com.liulishuo.filedownloader.util.FileDownloadHelper;

import java.io.IOException;
import java.io.InputStream;
import java.net.ProtocolException;
import java.util.List;
import java.util.Map;

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import okhttp3.ResponseBody;

/**
 * The FileDownloadConnection implemented with the okhttp3.
 */
public class OkHttp3Connection implements FileDownloadConnection {

    final OkHttpClient mClient;
    private final Request.Builder mRequestBuilder;

    private Request mRequest;
    private Response mResponse;

    OkHttp3Connection(Request.Builder builder, OkHttpClient client) {
        mRequestBuilder = builder;
        mClient = client;
    }

    public OkHttp3Connection(String url, OkHttpClient client) {
        this(new Request.Builder().url(url), client);
    }

    @Override
    public void addHeader(String name, String value) {
        mRequestBuilder.addHeader(name, value);
    }

    @Override
    public boolean dispatchAddResumeOffset(String etag, long offset) {
        return false;
    }

    @Override
    public InputStream getInputStream() throws IOException {
        if (mResponse == null) throw new IOException("Please invoke #execute first!");
        final ResponseBody body = mResponse.body();
        if (body == null) throw new IOException("No body found on response!");

        return body.byteStream();
    }

    @Override
    public Map> getRequestHeaderFields() {
        if (mRequest == null) {
            mRequest = mRequestBuilder.build();
        }

        return mRequest.headers().toMultimap();
    }

    @Override
    public Map> getResponseHeaderFields() {
        return mResponse == null ? null : mResponse.headers().toMultimap();
    }

    @Override
    public String getResponseHeaderField(String name) {
        return mResponse == null ? null : mResponse.header(name);
    }

    @Override public boolean setRequestMethod(String method) throws ProtocolException {
        mRequestBuilder.method(method, null);
        return true;
    }

    @Override
    public void execute() throws IOException {
        if (mRequest == null) {
            mRequest = mRequestBuilder.build();
        }

        mResponse = mClient.newCall(mRequest).execute();
    }

    @Override
    public int getResponseCode() throws IOException {
        if (mResponse == null) throw new IllegalStateException("Please invoke #execute first!");

        return mResponse.code();
    }

    @Override
    public void ending() {
        mRequest = null;
        mResponse = null;
    }

    /**
     * The creator for the connection implemented with the okhttp3.
     */
    public static class Creator implements FileDownloadHelper.ConnectionCreator {

        private OkHttpClient mClient;
        private OkHttpClient.Builder mBuilder;

        public Creator() {
        }

        /**
         * Create the Creator with the customized {@code client}.
         *
         * @param builder the builder for customizing the okHttp client.
         */
        public Creator(OkHttpClient.Builder builder) {
            mBuilder = builder;
        }

        /**
         * Get a non-null builder used for customizing the okHttpClient.
         * 

         * If you have already set a builder through the construct method, we will return it directly.
         *
         * @return the non-null builder.
         */
        public OkHttpClient.Builder customize() {
            if (mBuilder == null) {
                mBuilder = new OkHttpClient.Builder();
            }

            return mBuilder;
        }

        @Override
        public FileDownloadConnection create(String url) throws IOException {
            if (mClient == null) {
                synchronized (Creator.class) {
                    if (mClient == null) {
                        mClient = mBuilder != null ? mBuilder.build() : new OkHttpClient();
                        mBuilder = null;
                    }
                }
            }

            return new OkHttp3Connection(url, mClient);
        }
    }
}

在Application中注册

        //下载器初始化, 使用okhttp下载引擎
        FileDownloader.setupOnApplicationOnCreate(this).connectionCreator(new OkHttp3Connection.Creator(SSLUtils.createOkHttp()));

创建Okhttp实例并忽略SSL验证

    /**
     * filedownload 使用okhttp作为下载引擎忽略掉SSL验证, 添加证书不好使
     * @return
     */
    public static OkHttpClient.Builder createOkHttp() {

        OkHttpClient.Builder builder = new OkHttpClient.Builder();
        builder.connectTimeout(20_000, TimeUnit.SECONDS);
        builder.sslSocketFactory(SSLUtils.createSSLSocketFactory(), new X509TrustManager() {
            @Override
            public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {

            }

            @Override
            public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {

            }

            @Override
            public X509Certificate[] getAcceptedIssuers() {
                return new X509Certificate[0];
            }
        });
        builder.hostnameVerifier(new HostnameVerifier() {
            @Override
            public boolean verify(String hostname, SSLSession session) {
                return true;
            }
        });

        return builder;
    }

四：总结

    记录自己解决问题的点滴，感谢FileDownload的作者的答复，如果有遇到此问题的同胞，希望可以帮到你。

    祝：工作顺利！