Add ability to set non-global proxy

* Added a Proxy and proxy username/password to BoxAPIConnection.java
* Added support for opening the URL connection using this proxy if it
  exists in BoxAPIRequest.java

Closes #136.

Author: Derek Lansing

build.gradle

@@ -16,6 +16,7 @@ repositories {
 
 dependencies {
     compile 'com.eclipsesource.minimal-json:minimal-json:0.9.1'
+    compile 'commons-codec:commons-codec:1.10'
     testCompile 'junit:junit:4.11'
     testCompile 'org.hamcrest:hamcrest-library:1.3'
     testCompile 'com.github.tomakehurst:wiremock:1.52'

src/main/java/com/box/sdk/BoxAPIConnection.java

@@ -1,6 +1,7 @@
 package com.box.sdk;
 
 import java.net.MalformedURLException;
+import java.net.Proxy;
 import java.net.URL;
 import java.util.ArrayList;
 import java.util.List;
@@ -41,6 +42,10 @@ public class BoxAPIConnection {
     private volatile long lastRefresh;
     private volatile long expires;
 
+    private Proxy proxy;
+    private String proxyUsername;
+    private String proxyPassword;
+
     private String userAgent;
     private String accessToken;
     private String refreshToken;
@@ -330,6 +335,54 @@ public void setMaxRequestAttempts(int attempts) {
         this.maxRequestAttempts = attempts;
     }
 
+    /**
+     * Gets the proxy value to use for API calls to Box.
+     * @return current proxy value
+     */
+    public Proxy getProxy() {
+        return this.proxy;
+    }
+
+    /**
+     * Sets the Proxy to use for API calls to Box.
+     * @param proxy the current Proxy
+     */
+    public void setProxy(Proxy proxy) {
+        this.proxy = proxy;
+    }
+
+    /**
+     * Gets the username to use for a Proxy that requires basic auth.
+     * @return username to use for a Proxy that requires basic auth
+     */
+    public String getProxyUsername() {
+        return this.proxyUsername;
+    }
+
+    /**
+     * Sets the username to use for a Proxy that requires basic auth.
+     * @param proxyUsername username to use for a Proxy that requires basic auth
+     */
+    public void setProxyUsername(String proxyUsername) {
+        this.proxyUsername = proxyUsername;
+    }
+
+    /**
+     * Gets the password to use for a Proxy that requires basic auth.
+     * @return password to use for a Proxy that requires basic auth
+     */
+    public String getProxyPassword() {
+        return this.proxyPassword;
+    }
+
+    /**
+     * Sets the password to use for a Proxy that requires basic auth.
+     * @param proxyPassword password to use for a Proxy that requires basic auth
+     */
+    public void setProxyPassword(String proxyPassword) {
+        this.proxyPassword = proxyPassword;
+    }
+
     /**
      * Determines if this connection's access token can be refreshed. An access token cannot be refreshed if a refresh
      * token was never set.

src/main/java/com/box/sdk/BoxAPIRequest.java

@@ -14,6 +14,9 @@
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
+import org.apache.commons.codec.binary.Base64;
+
+
 /**
  * Used to make HTTP requests to the Box API.
  *
@@ -349,6 +352,13 @@ private BoxAPIResponse trySend(ProgressListener listener) {
         if (this.api != null) {
             connection.addRequestProperty("Authorization", "Bearer " + this.api.lockAccessToken());
             connection.setRequestProperty("User-Agent", this.api.getUserAgent());
+            if (this.api.getProxy() != null) {
+                if (this.api.getProxyUsername() != null && this.api.getProxyPassword() != null) {
+                    String usernameAndPassword = this.api.getProxyUsername() + ":" + this.api.getProxyPassword();
+                    String encoded = new String(Base64.encodeBase64(usernameAndPassword.getBytes()));
+                    connection.addRequestProperty("Proxy-authorization", "Basic " + encoded);
+                }
+            }
 
             if (this.api instanceof SharedLinkAPIConnection) {
                 SharedLinkAPIConnection sharedItemAPI = (SharedLinkAPIConnection) this.api;
@@ -447,7 +457,11 @@ private HttpURLConnection createConnection() {
         HttpURLConnection connection = null;
 
         try {
-            connection = (HttpURLConnection) this.url.openConnection();
+            if (this.api == null || this.api.getProxy() == null) {
+                connection = (HttpURLConnection) this.url.openConnection();
+            } else {
+                connection = (HttpURLConnection) this.url.openConnection(this.api.getProxy());
+            }
         } catch (IOException e) {
             throw new BoxAPIException("Couldn't connect to the Box API due to a network error.", e);
         }