https图片下载问题

https请求 http请求异常

unable to find valid certification path to requested target
问题
原因 缺少证书

使用以下工具生成jssecacerts文件
参考这篇 https://jingyan.baidu.com/article/6079ad0eb794a828ff86db08.html

import java.io.BufferedReader;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.io.OutputStream;

import java.security.KeyStore;

import java.security.MessageDigest;

import java.security.cert.CertificateException;

import java.security.cert.X509Certificate;

import javax.net.ssl.SSLContext;

import javax.net.ssl.SSLException;

import javax.net.ssl.SSLSocket;

import javax.net.ssl.SSLSocketFactory;

import javax.net.ssl.TrustManager;

import javax.net.ssl.TrustManagerFactory;

import javax.net.ssl.X509TrustManager;

/**

 * 安装证书

 *

 * @author   单红宇(365384722)

 * @myblog  http://blog.csdn.net/catoop/

 * @create    2016年4月14日

 */

public class CreateBook {

    // 我们要访问的HTTPS服务，如访问 https://www.shanhy.com

    public static final String hostName = "www.cwb.gov.tw";

    public static void main(String[] args) throws Exception {

        args = new String[]{hostName};

        String host;

        int port;

        char[] passphrase;

        if ((args.length == 1) || (args.length == 2)) {

            String[] c = args[0].split(":");

            host = c[0];

            port = (c.length == 1) ? 443 : Integer.parseInt(c[1]);

            String p = (args.length == 1) ? "changeit" : args[1];

            passphrase = p.toCharArray();

        } else {

            System.out.println("Usage: java InstallCert [:port] [passphrase]");

            return;

        }

        File file = new File("jssecacerts");

        if (file.isFile() == false) {

            char SEP = File.separatorChar;

            File dir = new File(System.getProperty("java.home") + SEP + "lib" + SEP + "security");

            file = new File(dir, "jssecacerts");

            if (file.isFile() == false) {

                file = new File(dir, "cacerts");

            }

        }

        System.out.println("Loading KeyStore " + file + "...");

        InputStream in = new FileInputStream(file);

        KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType());

        ks.load(in, passphrase);

        in.close();

        SSLContext context = SSLContext.getInstance("TLS");

        TrustManagerFactory tmf = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());

        tmf.init(ks);

        X509TrustManager defaultTrustManager = (X509TrustManager) tmf.getTrustManagers()[0];

        SavingTrustManager tm = new SavingTrustManager(defaultTrustManager);

        context.init(null, new TrustManager[] { tm }, null);

        SSLSocketFactory factory = context.getSocketFactory();

        System.out.println("Opening connection to " + host + ":" + port + "...");

        SSLSocket socket = (SSLSocket) factory.createSocket(host, port);

        socket.setSoTimeout(10000);

        try {

            System.out.println("Starting SSL handshake...");

            socket.startHandshake();

            socket.close();

            System.out.println();

            System.out.println("No errors, certificate is already trusted");

        } catch (SSLException e) {

            System.out.println();

            e.printStackTrace(System.out);

        }

        X509Certificate[] chain = tm.chain;

        if (chain == null) {

            System.out.println("Could not obtain server certificate chain");

            return;

        }

        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        System.out.println();

        System.out.println("Server sent " + chain.length + " certificate(s):");

        System.out.println();

        MessageDigest sha1 = MessageDigest.getInstance("SHA1");

        MessageDigest md5 = MessageDigest.getInstance("MD5");

        for (int i = 0; i < chain.length; i++) {

            X509Certificate cert = chain[i];

            System.out.println(" " + (i + 1) + " Subject " + cert.getSubjectDN());

            System.out.println("   Issuer  " + cert.getIssuerDN());

            sha1.update(cert.getEncoded());

            System.out.println("   sha1    " + toHexString(sha1.digest()));

            md5.update(cert.getEncoded());

            System.out.println("   md5     " + toHexString(md5.digest()));

            System.out.println();

        }

        System.out.println("Enter certificate to add to trusted keystore or 'q' to quit: [1]");

        String line = reader.readLine().trim();

        int k;

        try {

            k = (line.length() == 0) ? 0 : Integer.parseInt(line) - 1;

        } catch (NumberFormatException e) {

            System.out.println("KeyStore not changed");

            return;

        }

        X509Certificate cert = chain[k];

        String alias = host + "-" + (k + 1);

        ks.setCertificateEntry(alias, cert);

        OutputStream out = new FileOutputStream("jssecacerts");

        ks.store(out, passphrase);

        out.close();

        System.out.println();

        System.out.println(cert);

        System.out.println();

        System.out.println("Added certificate to keystore 'jssecacerts' using alias '" + alias + "'");

    }

    private static final char[] HEXDIGITS = "0123456789abcdef".toCharArray();

    private static String toHexString(byte[] bytes) {

        StringBuilder sb = new StringBuilder(bytes.length * 3);

        for (int b : bytes) {

            b &= 0xff;

            sb.append(HEXDIGITS[b >> 4]);

            sb.append(HEXDIGITS[b & 15]);

            sb.append(' ');

        }

        return sb.toString();

    }

    private static class SavingTrustManager implements X509TrustManager {

        private final X509TrustManager tm;

        private X509Certificate[] chain;

        SavingTrustManager(X509TrustManager tm) {

            this.tm = tm;

        }

        public X509Certificate[] getAcceptedIssuers() {

            throw new UnsupportedOperationException();

        }

        public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {

            throw new UnsupportedOperationException();

        }

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

            this.chain = chain;

            tm.checkServerTrusted(chain, authType);

        }

    }

}

主类运行后依据提示 按个1

生成的证书放置目录：
$JAVA_HOME\jre\lib\security
参考http://blog.csdn.net/cece0926/article/details/8258628
我装了2个jdk 系统环境变量里是1.8 但是eclipse里面用的是1.7 ，之前改了1.8的不行。得改1.7的。

总结
访问下载https的url图片需配置访问证书， $JAVA_HOME/jre/lib/security/ 路径下添加了jssecacerts文件。该文件由 以上类创建。同时注意linux环境下需修改文件访问权限及项目中目录路径 / 分隔

图片下载测试代码：

import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

import com.ym.utils.DownUtil;

public class Test {
    private static final String SAVEPATH;
    static {
        // 兼容linux部署环境
            if (System.getProperty("os.name").contains("Windows")){
                SAVEPATH= "//10.153.xx.xx/data/xx/";
            }else {
                 SAVEPATH=  "/data/webapp_share/xx/";
            }
    }

     public static void main(String[] args) {

          String url = "https://xx/xx/HD_Radar/xx.png";
            //downloadPicture(url);
            try {
                download(url,"down.png",SAVEPATH);
            } catch (Exception e) {
                e.printStackTrace();
            }

        }
        //链接url下载图片
        private static void downloadPicture(String urlList) {
            URL url = null;
            int imageNumber = 0;

            try {
                url = new URL(urlList);
                DataInputStream dataInputStream = new DataInputStream(url.openStream());

                String imageName =  "F:/test.jpg";

                FileOutputStream fileOutputStream = new FileOutputStream(new File(imageName));
                ByteArrayOutputStream output = new ByteArrayOutputStream();

                byte[] buffer = new byte[1024];
                int length;

                while ((length = dataInputStream.read(buffer)) > 0) {
                    output.write(buffer, 0, length);
                }
                byte[] context=output.toByteArray();
                fileOutputStream.write(output.toByteArray());
                dataInputStream.close();
                fileOutputStream.close();
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        public static void download(String urlString, String filename, String savePath) throws Exception {
            // 构造URL
            URL url = new URL(urlString);
            // 打开连接
            URLConnection con = url.openConnection();
            // 设置请求超时为5s
            con.setConnectTimeout(5 * 1000);
            // 输入流
            InputStream is = con.getInputStream(); // unable to find valid certification path to requested target  缺少安全证书

            // 1K的数据缓冲
            byte[] bs = new byte[1024];
            // 读取到的数据长度
            int len;
            // 输出的文件流
            File sf = new File(savePath);
            if (!sf.exists()) {
                sf.mkdirs();
            }
            OutputStream os = new FileOutputStream(sf.getPath() + "/" + filename);
            // 开始读取
            while ((len = is.read(bs)) != -1) {
                os.write(bs, 0, len);
            }
            // 完毕，关闭所有链接
            os.flush();
            os.close();
            is.close();
        }
}