Move TLS certificates.

- Move certificates to src/main/resources folder.
- Update the code that loads the certificates to make use of Java's resources API.

integration-testing/src/main/java/io/grpc/testing/integration/TestServiceClient.java

@@ -216,10 +216,8 @@ public class TestServiceClient {
         SslContext sslContext = null;
         if (useTestCa) {
           try {
-            String dir = "integration-testing/certs";
-            sslContext = SslContext.newClientContext(
-                new File(dir + "/ca.pem"));
-          } catch (SSLException ex) {
+            sslContext = SslContext.newClientContext(Util.loadCert("ca.pem"));
+          } catch (Exception ex) {
             throw new RuntimeException(ex);
           }
         }

integration-testing/src/main/java/io/grpc/testing/integration/TestServiceServer.java

@@ -134,10 +134,8 @@ public class TestServiceServer {
     executor = Executors.newSingleThreadScheduledExecutor();
     SslContext sslContext = null;
     if (useTls) {
-      String dir = "integration-testing/certs";
-      sslContext = SslContext.newServerContext(
-          new File(dir + "/server1.pem"),
-          new File(dir + "/server1.key"));
+      sslContext = SslContext.newServerContext(Util.loadCert("server1.pem"),
+                                               Util.loadCert("server1.key"));
     }
     server = NettyServerBuilder.forPort(port)
         .sslContext(sslContext)

integration-testing/src/main/java/io/grpc/testing/integration/Util.java

@@ -38,7 +38,12 @@ import io.grpc.proto.ProtoUtils;
 
 import org.junit.Assert;
 
+import java.io.BufferedWriter;
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.FileWriter;
 import java.io.IOException;
+import java.io.InputStream;
 import java.net.ServerSocket;
 import java.util.List;
 
@@ -54,9 +59,8 @@ public class Util {
    * Picks an unused port.
    */
   public static int pickUnusedPort() {
-    ServerSocket serverSocket = null;
     try {
-      serverSocket = new ServerSocket(0);
+      ServerSocket serverSocket = new ServerSocket(0);
       int port = serverSocket.getLocalPort();
       serverSocket.close();
       return port;
@@ -65,6 +69,29 @@ public class Util {
     }
   }
 
+  /**
+   * Load a file from the resources folder.
+   *
+   * @param name  name of a file in src/main/resources/certs.
+   */
+  public static File loadCert(String name) throws IOException {
+    InputStream in = Util.class.getResourceAsStream("/certs/" + name);
+    File tmpFile = File.createTempFile(name, "");
+    tmpFile.deleteOnExit();
+
+    BufferedWriter writer = new BufferedWriter(new FileWriter(tmpFile));
+    try {
+      int b;
+      while ((b = in.read()) != -1) {
+        writer.write(b);
+      }
+    } finally {
+      writer.close();
+    }
+
+    return tmpFile;
+  }
+
   public static void assertEquals(MessageLite expected, MessageLite actual) {
     if (expected == null || actual == null) {
       Assert.assertEquals(expected, actual);