1. import java.io.File;  
2. import java.io.FileNotFoundException;  
3. import java.io.FileOutputStream;  
4. import java.io.IOException;  
5. import java.io.InputStream;  
6. import java.io.OutputStream;  
7. import java.net.MalformedURLException;  
8. import java.net.URL;  
9. import java.net.URLConnection;  
10. import java.util.Iterator;  
11.   
12. import javax.imageio.ImageIO;  
13. import javax.imageio.ImageReader;  
14. import javax.imageio.stream.ImageInputStream;  
15.   
16.   
17. public class TestDownLoadImage {  
18.       
19.     public static void main(String[] args) {  
20.          String url="http://wx1.sinaimg.cn/mw690/006sl6kBgy1fel3aq0nyej30i20hxq7i.jpg";  
21.          String downToFilePath="d:/download/image/";  
22.          String fileName="test";  
23.          imageDownLoad(url, downToFilePath,fileName);  
24.           
25.     }  
26.     public static void  imageDownLoad(String urlString, String filepath,String filename) {  
27.           
28.         InputStream is =null;  
29.         ImageInputStream iis=null;  
30.         OutputStream os =null;  
31.         String downloadPath=null;  
32.         try {  
33.               
34.             URL url = new URL(urlString);  
35.             URLConnection con = url.openConnection();  
36.             is = con.getInputStream();  
37.             iis=ImageIO.createImageInputStream(is);  
38.             Iterator<ImageReader> iter = ImageIO.getImageReaders(iis);    
39.             if (!iter.hasNext()) {    
40.                 return  ;    
41.             }    
42.             ImageReader reader = iter.next();    
43.              //Read file format jpg, etc.  
44.             String imgFormat=reader.getFormatName();    
45.             byte[] bs = new byte[1024];  
46.             int len;  
47.             File file=new File(filepath);  
48.             if(!file.exists()){           
49.                 file.mkdir();  
50.             }  
51.             downloadPath=filepath+"//"+filename+"."+imgFormat;  
52.             os = new FileOutputStream(downloadPath);  
53.             while ((len = iis.read(bs)) != -1) {  
54.               os.write(bs, 0, len);  
55.             }  
56.         } catch (MalformedURLException e) {  
57.             e.printStackTrace();  
58.         } catch (FileNotFoundException e) {  
59.             e.printStackTrace();  
60.         } catch (IOException e) {  
61.             e.printStackTrace();  
62.         }  
63.         finally{  
64.             try {  
65.                 os.close();  
66.                 is.close();  
67.                 iis.close();  
68.             } catch (IOException e) {  
69.                 e.printStackTrace();  
70.             }   
71.         }  
72.         return ;  
73.     }     
74.   
75. }  

This code can download pictures normally. No problem.


Later, I came across an image whose address was https, String url="https://05.imgmini.eastday.com/mobile/20170413/20170413053046_4a5e70ed0b39c824517630e6954861f2_1.jpeg";

The code is wrong.

Report errors:

1. javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target  
2.     at com.sun.net.ssl.internal.ssl.Alerts.getSSLException(Alerts.java:174)  
3.     at com.sun.net.ssl.internal.ssl.SSLSocketImpl.fatal(SSLSocketImpl.java:1747)  
4.     at com.sun.net.ssl.internal.ssl.Handshaker.fatalSE(Handshaker.java:241)  
5.     at com.sun.net.ssl.internal.ssl.Handshaker.fatalSE(Handshaker.java:235)  
6.     at com.sun.net.ssl.internal.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1209)  
7.     at com.sun.net.ssl.internal.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:135)  
8.     at com.sun.net.ssl.internal.ssl.Handshaker.processLoop(Handshaker.java:593)  
9.     at com.sun.net.ssl.internal.ssl.Handshaker.process_record(Handshaker.java:529)  
10.     at com.sun.net.ssl.internal.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:943)  
11.     at com.sun.net.ssl.internal.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1188)  
12.     at com.sun.net.ssl.internal.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1215)  
13.     at com.sun.net.ssl.internal.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1199)  
14.     at sun.net.www.protocol.https.HttpsClient.afterConnect(HttpsClient.java:434)  
15.     at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:166)  
16.     at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1195)  
17.     at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:234)  
18.     at TestDownLoadImage.imageDownLoad(TestDownLoadImage.java:43)  
19.     at TestDownLoadImage.main(TestDownLoadImage.java:30)  
20. Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target  
21.     at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:323)  
22.     at sun.security.validator.PKIXValidator.engineValidate(PKIXValidator.java:217)  
23.     at sun.security.validator.Validator.validate(Validator.java:218)  
24.     at com.sun.net.ssl.internal.ssl.X509TrustManagerImpl.validate(X509TrustManagerImpl.java:126)  
25.     at com.sun.net.ssl.internal.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:209)  
26.     at com.sun.net.ssl.internal.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:249)  
27.     at com.sun.net.ssl.internal.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1188)  
28.     ... 13 more  
29. Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target  
30.     at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(SunCertPathBuilder.java:174)  
31.     at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:238)  
32.     at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:318)  
33.     ... 19 more  
34. Exception in thread "main" java.lang.NullPointerException  
35.     at TestDownLoadImage.imageDownLoad(TestDownLoadImage.java:72)  
36.     at TestDownLoadImage.main(TestDownLoadImage.java:30)  

Looking up the information on the Internet is a certificate problem, you can write a logic in the code to ignore the certificate:

Here is the code downloaded online: http://www.sojson.com/blog/195.html

1. import java.security.cert.CertificateException;  
2. import java.security.cert.X509Certificate;  
3.    
4. import javax.net.ssl.HostnameVerifier;  
5. import javax.net.ssl.HttpsURLConnection;  
6. import javax.net.ssl.SSLContext;  
7. import javax.net.ssl.SSLSession;  
8. import javax.net.ssl.TrustManager;  
9. import javax.net.ssl.X509TrustManager;  
10.    
11. public class SslUtils {  
12.    
13.     public static void trustAllHttpsCertificates() throws Exception {  
14.         TrustManager[] trustAllCerts = new TrustManager[1];  
15.         TrustManager tm = new miTM();  
16.         trustAllCerts[0] = tm;  
17.         SSLContext sc = SSLContext.getInstance("SSL");  
18.         sc.init(null, trustAllCerts, null);  
19.         HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());  
20.     }  
21.    
22.     static class miTM implements TrustManager,X509TrustManager {  
23.         public X509Certificate[] getAcceptedIssuers() {  
24.             return null;  
25.         }  
26.    
27.         public boolean isServerTrusted(X509Certificate[] certs) {  
28.             return true;  
29.         }  
30.    
31.         public boolean isClientTrusted(X509Certificate[] certs) {  
32.             return true;  
33.         }  
34.    
35.         public void checkServerTrusted(X509Certificate[] certs, String authType)  
36.                 throws CertificateException {  
37.             return;  
38.         }  
39.    
40.         public void checkClientTrusted(X509Certificate[] certs, String authType)  
41.                 throws CertificateException {  
42.             return;  
43.         }  
44.     }  
45.        
46.     /** 
47.      * The SSL certificate that ignores the HTTPS request must be invoked before openConnection 
48.      * @throws Exception 
49.      */  
50.     public static void ignoreSsl() throws Exception{  
51.         HostnameVerifier hv = new HostnameVerifier() {  
52.             public boolean verify(String urlHostName, SSLSession session) {  
53.                 return true;  
54.             }  
55.         };  
56.         trustAllHttpsCertificates();  
57.         HttpsURLConnection.setDefaultHostnameVerifier(hv);  
58.     }  
59. }  

//Use it before URLConnection con = url.openConnection()

1.     
2.   
3. public static void main(String[] args) {  
4.      //String url="http://wx1.sinaimg.cn/mw690/006sl6kBgy1fel3aq0nyej30i20hxq7i.jpg";  
5.      String url="https://05.imgmini.eastday.com/mobile/20170413/20170413053046_4a5e70ed0b39c824517630e6954861f2_1.jpeg";  
6.      String downToFilePath="d:/download/image/";  
7.      String fileName="test";  
8.      try {  
9.         SslUtils.ignoreSsl();  
10.     } catch (Exception e) {  
11.         e.printStackTrace();  
12.     }  
13.      imageDownLoad(url, downToFilePath,fileName);  
14.       
15. }