Add custom User-Agent for MapFishPrint.

This fixes
#1955

core/build.gradle

@@ -1,4 +1,5 @@
 import org.apache.tools.ant.taskdefs.condition.Os
+import org.apache.tools.ant.filters.*
 
 apply plugin: 'war'
 apply plugin: 'distribution'
@@ -217,6 +218,13 @@ def gitRevision() {
 compileJava.options.compilerArgs = ['-Xlint:deprecation', '-Xlint:unchecked']
 compileTestJava.options.compilerArgs = ['-Xlint:deprecation', '-Xlint:unchecked']
 
+// Add version to resources, used for User-Agent string:
+processResources {
+    filter ReplaceTokens, tokens: [
+        "application.version": version
+    ]
+}
+
 def addManifestAttribute(manifest) {
     manifest.mainAttributes(
             'Mapfish-Print-Version': version,

core/src/main/java/org/mapfish/print/http/MfClientHttpRequestFactoryImpl.java

@@ -85,7 +85,8 @@ private static CloseableHttpClient createHttpClient(final int maxConnTotal, fina
                 setDefaultCredentialsProvider(new MfCredentialsProvider()).
                 setDefaultRequestConfig(requestConfig).
                 setMaxConnTotal(maxConnTotal).
-                setMaxConnPerRoute(maxConnPerRoute);
+                setMaxConnPerRoute(maxConnPerRoute).
+                setUserAgent(UserAgentCreator.getUserAgent());
         return httpClientBuilder.build();
     }
 

core/src/main/java/org/mapfish/print/http/UserAgentCreator.java

@@ -0,0 +1,39 @@
+package org.mapfish.print.http;
+
+import org.apache.http.util.VersionInfo;
+
+/**
+ * Utility class for the creation of the User-Agent string.
+ * 
+ * @author bhoefling
+ *
+ */
+public final class UserAgentCreator {
+
+    private static final String AGENT_NAME = "MapFishPrint";
+
+    /**
+     * Private constructor.
+     */
+    private UserAgentCreator() {
+
+    }
+    /**
+     * Builds a User-Agent string.
+     * 
+     * @return User-Agent
+     */
+    public static String getUserAgent() {
+
+        final String httpClientUserAgent = VersionInfo.getUserAgent("Apache-HttpClient",
+                "org.apache.http.client", UserAgentCreator.class);
+
+        // This is based on the code from HttpClient:
+        final VersionInfo mapFishPrintVersionInfo = VersionInfo.loadVersionInfo("org.mapfish.print",
+                UserAgentCreator.class.getClassLoader());
+        final String mfpRelease = mapFishPrintVersionInfo.getRelease();
+
+        final String userAgent = String.format("%s/%s %s", AGENT_NAME, mfpRelease, httpClientUserAgent);
+        return userAgent;
+    }
+}

core/src/main/resources/org/mapfish/print/version.properties

@@ -0,0 +1,3 @@
+info.release=@application.version@
+info.module=MapFishPrint
+#info.timestamp=...