Add possibility to retry requests

Fixes #83

README.md

@@ -211,6 +211,8 @@ is interpreted as undefined. <em>(default: <code>-1</code>)</em></dd>
 <dd>The maximum time in milliseconds to wait for data from the server.
 A value of <code>0</code> (zero) means infinite timeout. A negative value
 is interpreted as undefined. <em>(default: <code>-1</code>)</em></dd>
+<dt>retries</dt>
+<dd>Specifies the maximum number of retry attempts if a request has failed. By default, requests are never retried and the task fails immediately if the first request does not succeed. If the value is greater than <code>0</code>, failed requests are retried regardless of the actual error. This includes failed connection attempts and file-not-found errors (404). A negative value means infinite retries. <em>(default: <code>0</code>)</em></dd>
 </dl>
 
 ### Authentication

src/main/java/de/undercouch/gradle/tasks/download/Download.java

@@ -188,6 +188,11 @@ public void readTimeout(int milliseconds) {
         action.readTimeout(milliseconds);
     }
 
+    @Override
+    public void retries(int retries) {
+        action.retries(retries);
+    }
+
     @Override
     public void downloadTaskDir(Object dir) {
         action.downloadTaskDir(dir);
@@ -283,6 +288,11 @@ public int getReadTimeout() {
         return action.getReadTimeout();
     }
 
+    @Override
+    public int getRetries() {
+        return action.getRetries();
+    }
+
     @Override
     public File getDownloadTaskDir() {
         return action.getDownloadTaskDir();

src/main/java/de/undercouch/gradle/tasks/download/DownloadAction.java

@@ -74,7 +74,7 @@ public class DownloadAction implements DownloadSpec {
             GradleVersion.version("2.0");
 
     private final Project project;
-    private List<URL> sources = new ArrayList<URL>(1);
+    private List<URL> sources = new ArrayList<>(1);
     private File dest;
     private boolean quiet = false;
     private boolean overwrite = true;
@@ -87,6 +87,7 @@ public class DownloadAction implements DownloadSpec {
     private boolean acceptAnyCertificate = false;
     private int connectTimeoutMs = -1;
     private int readTimeoutMs = -1;
+    private int retries = 0;
     private File downloadTaskDir;
     private boolean tempAndMove = false;
     private UseETag useETag = UseETag.FALSE;
@@ -244,7 +245,7 @@ private void executeHttpProtocol(URL src, HttpClientFactory clientFactory,
 
         //create HTTP client
         CloseableHttpClient client = clientFactory.createHttpClient(
-                httpHost, acceptAnyCertificate);
+                httpHost, acceptAnyCertificate, retries);
 
         //open URL connection
         String etag = null;
@@ -875,6 +876,11 @@ public void readTimeout(int milliseconds) {
         this.readTimeoutMs = milliseconds;
     }
 
+    @Override
+    public void retries(int retries) {
+        this.retries = retries;
+    }
+
     @Override
     public void downloadTaskDir(Object dir) {
         if (dir instanceof Closure) {
@@ -1002,6 +1008,11 @@ public int getReadTimeout() {
         return readTimeoutMs;
     }
 
+    @Override
+    public int getRetries() {
+        return retries;
+    }
+
     @Override
     public File getDownloadTaskDir() {
         return downloadTaskDir;

src/main/java/de/undercouch/gradle/tasks/download/DownloadSpec.java

@@ -132,6 +132,14 @@ public interface DownloadSpec {
      */
     void readTimeout(int milliseconds);
 
+    /**
+     * Specifies the maximum number of retry attempts if a request has failed.
+     * By default, requests are never retried and the task fails immediately if
+     * the first request does not succeed.
+     * @param retries the maximum number of retries (default: 0)
+     */
+    void retries(int retries);
+
     /**
      * Specifies the directory where gradle-download-task stores information
      * that should persist between builds
@@ -258,6 +266,11 @@ public interface DownloadSpec {
      * server
      */
     int getReadTimeout();
+
+    /**
+     * @return the maximum number of retries
+     */
+    int getRetries();
 
     /**
      * @return the directory where gradle-download-task stores information

src/main/java/de/undercouch/gradle/tasks/download/internal/CachingHttpClientFactory.java

@@ -20,6 +20,7 @@
 import java.io.IOException;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Objects;
 
 /**
  * An implementation of {@link HttpClientFactory} that caches created clients
@@ -31,11 +32,11 @@ public class CachingHttpClientFactory extends DefaultHttpClientFactory {
 
     @Override
     public CloseableHttpClient createHttpClient(HttpHost httpHost,
-            boolean acceptAnyCertificate) {
-        CacheKey key = new CacheKey(httpHost, acceptAnyCertificate);
+            boolean acceptAnyCertificate, int retries) {
+        CacheKey key = new CacheKey(httpHost, acceptAnyCertificate, retries);
         CloseableHttpClient c = cachedClients.get(key);
         if (c == null) {
-            c = super.createHttpClient(httpHost, acceptAnyCertificate);
+            c = super.createHttpClient(httpHost, acceptAnyCertificate, retries);
             cachedClients.put(key, c);
         }
         return c;
@@ -58,40 +59,31 @@ public void close() throws IOException {
     private static class CacheKey {
         private final HttpHost httpHost;
         private final boolean acceptAnyCertificate;
+        private final int retries;
 
-        CacheKey(HttpHost httpHost, boolean acceptAnyCertificate) {
+        CacheKey(HttpHost httpHost, boolean acceptAnyCertificate, int retries) {
             this.httpHost = httpHost;
             this.acceptAnyCertificate = acceptAnyCertificate;
+            this.retries = retries;
         }
 
         @Override
-        public int hashCode() {
-            final int prime = 31;
-            int result = 1;
-            result = prime * result + (acceptAnyCertificate ? 1231 : 1237);
-            result = prime * result + ((httpHost == null) ? 0 : httpHost.hashCode());
-            return result;
-        }
-
-        @Override
-        public boolean equals(Object obj) {
-            if (this == obj) {
+        public boolean equals(Object o) {
+            if (this == o) {
                 return true;
             }
-            if (obj == null) {
+            if (o == null || getClass() != o.getClass()) {
                 return false;
             }
-            if (getClass() != obj.getClass()) {
-                return false;
-            }
-            CacheKey other = (CacheKey)obj;
-            if (acceptAnyCertificate != other.acceptAnyCertificate) {
-                return false;
-            }
-            if (httpHost == null) {
-                return other.httpHost == null;
-            }
-            return httpHost.equals(other.httpHost);
+            CacheKey cacheKey = (CacheKey)o;
+            return acceptAnyCertificate == cacheKey.acceptAnyCertificate &&
+                    retries == cacheKey.retries &&
+                    httpHost.equals(cacheKey.httpHost);
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(httpHost, acceptAnyCertificate, retries);
         }
     }
 }

src/main/java/de/undercouch/gradle/tasks/download/internal/DefaultHttpClientFactory.java

@@ -15,6 +15,7 @@
 package de.undercouch.gradle.tasks.download.internal;
 
 import de.undercouch.gradle.tasks.download.org.apache.http.HttpHost;
+import de.undercouch.gradle.tasks.download.org.apache.http.client.HttpRequestRetryHandler;
 import de.undercouch.gradle.tasks.download.org.apache.http.config.Registry;
 import de.undercouch.gradle.tasks.download.org.apache.http.config.RegistryBuilder;
 import de.undercouch.gradle.tasks.download.org.apache.http.conn.HttpClientConnectionManager;
@@ -25,17 +26,19 @@
 import de.undercouch.gradle.tasks.download.org.apache.http.impl.client.HttpClientBuilder;
 import de.undercouch.gradle.tasks.download.org.apache.http.impl.conn.BasicHttpClientConnectionManager;
 import de.undercouch.gradle.tasks.download.org.apache.http.impl.conn.SystemDefaultRoutePlanner;
+import de.undercouch.gradle.tasks.download.org.apache.http.protocol.HttpContext;
 
 import javax.net.ssl.HostnameVerifier;
 import javax.net.ssl.SSLContext;
 import javax.net.ssl.TrustManager;
+import java.io.IOException;
 import java.security.KeyManagementException;
 import java.security.NoSuchAlgorithmException;
 import java.security.SecureRandom;
 
 /**
  * Default implementation of {@link HttpClientFactory}. Creates a new client
- * every time {@link #createHttpClient(HttpHost, boolean)}
+ * every time {@link #createHttpClient(HttpHost, boolean, int)}
  * is called. The caller is responsible for closing this client.
  * @author Michel Kraemer
  */
@@ -49,9 +52,21 @@ public class DefaultHttpClientFactory implements HttpClientFactory {
 
     @Override
     public CloseableHttpClient createHttpClient(HttpHost httpHost,
-            boolean acceptAnyCertificate) {
+            boolean acceptAnyCertificate, final int retries) {
         HttpClientBuilder builder = HttpClientBuilder.create();
-
+
+        //configure retries
+        if (retries == 0) {
+            builder.disableAutomaticRetries();
+        } else {
+            builder.setRetryHandler(new HttpRequestRetryHandler() {
+                @Override
+                public boolean retryRequest(IOException e, int i, HttpContext httpContext) {
+                    return retries < 0 || i <= retries;
+                }
+            });
+        }
+
         //configure proxy from system environment
         builder.setRoutePlanner(new SystemDefaultRoutePlanner(null));
 

src/main/java/de/undercouch/gradle/tasks/download/internal/HttpClientFactory.java

@@ -28,8 +28,9 @@ public interface HttpClientFactory {
      * @param acceptAnyCertificate true if HTTPS certificate verification
      * errors should be ignored and any certificate (even an invalid one)
      * should be accepted
+     * @param retries the number of retries to perform if an HTTP request fails
      * @return the HTTP client
      */
     CloseableHttpClient createHttpClient(HttpHost httpHost,
-            boolean acceptAnyCertificate);
+            boolean acceptAnyCertificate, int retries);
 }