版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/u010248330/article/details/70161899
[java] view plain copy import java.io.File; import java.io.FileNotFoundException; 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 java.util.Iterator; import javax.imageio.ImageIO; import javax.imageio.ImageReader; import javax.imageio.stream.ImageInputStream; public class TestDownLoadImage { public static void main(String[] args) { String url="http://wx1.sinaimg.cn/mw690/006sl6kBgy1fel3aq0nyej30i20hxq7i.jpg"; String downToFilePath="d:/download/image/"; String fileName="test"; imageDownLoad(url, downToFilePath,fileName); } public static void imageDownLoad(String urlString, String filepath,String filename) { InputStream is =null; ImageInputStream iis=null; OutputStream os =null; String downloadPath=null; try { URL url = new URL(urlString); URLConnection con = url.openConnection(); is = con.getInputStream(); iis=ImageIO.createImageInputStream(is); Iterator<ImageReader> iter = ImageIO.getImageReaders(iis); if (!iter.hasNext()) { return ; } ImageReader reader = iter.next(); //读文件格式jpg 等 String imgFormat=reader.getFormatName(); byte[] bs = new byte[1024]; int len; File file=new File(filepath); if(!file.exists()){ file.mkdir(); } downloadPath=filepath+"//"+filename+"."+imgFormat; os = new FileOutputStream(downloadPath); while ((len = iis.read(bs)) != -1) { os.write(bs, 0, len); } } catch (MalformedURLException e) { e.printStackTrace(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally{ try { os.close(); is.close(); iis.close(); } catch (IOException e) { e.printStackTrace(); } } return ; } }这个代码是可以正常下载图片的。没有出问题。后来遇到一个图片的地址是https的，String url="https://05.imgmini.eastday.com/mobile/20170413/20170413053046_4a5e70ed0b39c824517630e6954861f2_1.jpeg";代码就报错了。
报错：
[plain] view plain copy 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 at com.sun.net.ssl.internal.ssl.Alerts.getSSLException(Alerts.java:174) at com.sun.net.ssl.internal.ssl.SSLSocketImpl.fatal(SSLSocketImpl.java:1747) at com.sun.net.ssl.internal.ssl.Handshaker.fatalSE(Handshaker.java:241) at com.sun.net.ssl.internal.ssl.Handshaker.fatalSE(Handshaker.java:235) at com.sun.net.ssl.internal.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1209) at com.sun.net.ssl.internal.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:135) at com.sun.net.ssl.internal.ssl.Handshaker.processLoop(Handshaker.java:593) at com.sun.net.ssl.internal.ssl.Handshaker.process_record(Handshaker.java:529) at com.sun.net.ssl.internal.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:943) at com.sun.net.ssl.internal.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1188) at com.sun.net.ssl.internal.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1215) at com.sun.net.ssl.internal.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1199) at sun.net.www.protocol.https.HttpsClient.afterConnect(HttpsClient.java:434) at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:166) at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1195) at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:234) at TestDownLoadImage.imageDownLoad(TestDownLoadImage.java:43) at TestDownLoadImage.main(TestDownLoadImage.java:30) Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:323) at sun.security.validator.PKIXValidator.engineValidate(PKIXValidator.java:217) at sun.security.validator.Validator.validate(Validator.java:218) at com.sun.net.ssl.internal.ssl.X509TrustManagerImpl.validate(X509TrustManagerImpl.java:126) at com.sun.net.ssl.internal.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:209) at com.sun.net.ssl.internal.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:249) at com.sun.net.ssl.internal.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1188) ... 13 more Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(SunCertPathBuilder.java:174) at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:238) at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:318) ... 19 more Exception in thread "main" java.lang.NullPointerException at TestDownLoadImage.imageDownLoad(TestDownLoadImage.java:72) at TestDownLoadImage.main(TestDownLoadImage.java:30) 在网上查阅了信息说是证书问题，可以在代码中写一段逻辑忽略证书： 下面是网上下载的代码：http://www.sojson.com/blog/195.html [java] view plain copy import java.security.cert.CertificateException; import java.security.cert.X509Certificate; import javax.net.ssl.HostnameVerifier; import javax.net.ssl.HttpsURLConnection; import javax.net.ssl.SSLContext; import javax.net.ssl.SSLSession; import javax.net.ssl.TrustManager; import javax.net.ssl.X509TrustManager; public class SslUtils { public 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 { public X509Certificate[] getAcceptedIssuers() { return null; } public boolean isServerTrusted(X509Certificate[] certs) { return true; } public boolean isClientTrusted(X509Certificate[] certs) { return true; } public void checkServerTrusted(X509Certificate[] certs, String authType) throws CertificateException { return; } 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 * @throws Exception */ public static void ignoreSsl() throws Exception{ HostnameVerifier hv = new HostnameVerifier() { public boolean verify(String urlHostName, SSLSession session) { return true; } }; trustAllHttpsCertificates(); HttpsURLConnection.setDefaultHostnameVerifier(hv); } } //在URLConnection con = url.openConnection()之前使用就行 [java] view plain copy public static void main(String[] args) { //String url="http://wx1.sinaimg.cn/mw690/006sl6kBgy1fel3aq0nyej30i20hxq7i.jpg"; String url="https://05.imgmini.eastday.com/mobile/20170413/20170413053046_4a5e70ed0b39c824517630e6954861f2_1.jpeg"; String downToFilePath="d:/download/image/"; String fileName="test"; try { SslUtils.ignoreSsl(); } catch (Exception e) { e.printStackTrace(); } imageDownLoad(url, downToFilePath,fileName); }