PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilder

java程序在访问https资源时，出现报错

sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target

下面给出解决方案(忽略证书信任)

    private static final String FILE_TO = "d:\\download\\test.pdf";

    @Test
    void testHttpsUrl() throws IOException {
    
    
        String url = "https://luomo-oss.oss-cn-beijing.aliyuncs.com/Druid%20%E4%BD%BF%E7%94%A8%E6%89%8B%E5%86%8C.pdf";
        InputStream inputStream = null;
        try{
    
    
            URL encodedUrl = new URL(url);
            if("https".equals(encodedUrl.getProtocol())){
    
    
                SslUtil.ignoreSsl();
            }
            inputStream = encodedUrl.openConnection().getInputStream();
        }catch (Exception e){
    
    
            e.printStackTrace();
        }
        File file = new File(FILE_TO);
        try (FileOutputStream outputStream = new FileOutputStream(file)) {
    
    
            int read;
            byte[] bytes = new byte[1024];
            while ((read = inputStream.read(bytes)) != -1) {
    
    
                outputStream.write(bytes, 0, read);
            }
        }
    }

SslUtil

import javax.net.ssl.*;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

public class SslUtil {
    
    

    private static void trustAllHttpsCertificates() throws Exception {
    
    
        TrustManager[] trustAllCerts = new TrustManager[1];
        TrustManager tm = new miTM();
        trustAllCerts[0] = tm;
        SSLContext sc = SSLContext.getInstance("SSL");
        sc.init(null, trustAllCerts, null);
        HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());
    }

    static class miTM implements TrustManager, X509TrustManager {
    
    

        @Override
        public X509Certificate[] getAcceptedIssuers() {
    
    
            return null;
        }

        public boolean isServerTrusted(X509Certificate[] certs) {
    
    
            return true;
        }

        public boolean isClientTrusted(X509Certificate[] certs) {
    
    
            return true;
        }

        @Override
        public void checkServerTrusted(X509Certificate[] certs, String authType) {
    
    
            return;
        }

        @Override
        public void checkClientTrusted(X509Certificate[] certs, String authType)
                throws CertificateException {
    
    
            return;
        }
    }

    /**
     * 忽略HTTPS请求的SSL证书，必须在openConnection之前调用
     */
    public static void ignoreSsl() throws Exception{
    
    
        HostnameVerifier hv = (urlHostName, session) -> true;
        trustAllHttpsCertificates();
        HttpsURLConnection.setDefaultHostnameVerifier(hv);
    }
}