Use multiple get operations in Servlet cache query (#3263)

frameworks/Java/servlet/src/main/java/hello/Cache2kPostgresServlet.java

@@ -1,14 +1,17 @@
 package hello;
 
-import java.io.*;
-import java.sql.*;
-import java.util.*;
-import java.util.concurrent.*;
+import java.io.IOException;
+import java.sql.SQLException;
+import java.util.Map;
+import java.util.concurrent.ThreadLocalRandom;
 
-import javax.annotation.*;
-import javax.servlet.*;
-import javax.servlet.http.*;
-import javax.sql.*;
+import javax.annotation.Resource;
+import javax.servlet.ServletConfig;
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import javax.sql.DataSource;
 
 import org.cache2k.Cache;
 import org.cache2k.Cache2kBuilder;
@@ -20,7 +23,7 @@ import org.cache2k.Cache2kBuilder;
 public class Cache2kPostgresServlet extends HttpServlet {
 	// Database details.
 	private static final int DB_ROWS = 10000;
-	
+
 	// Database connection pool.
 	@Resource(name = "jdbc/hello_world")
 	private DataSource dataSource;
@@ -36,13 +39,10 @@ public class Cache2kPostgresServlet extends HttpServlet {
 		} catch (SQLException e) {
 			throw new ServletException(e);
 		}
-		
+
 		// Build the cache
-		cache = new Cache2kBuilder<Integer, CachedWorld>() {}
-		    .name("cachedWorld")
-		    .eternal(true)
-		    .entryCapacity(DB_ROWS)
-		    .build();
+		cache = new Cache2kBuilder<Integer, CachedWorld>() {
+		}.name("cachedWorld").eternal(true).entryCapacity(DB_ROWS).build();
 		cache.putAll(worlds);
 	}
 
@@ -50,18 +50,16 @@ public class Cache2kPostgresServlet extends HttpServlet {
 	protected void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException,
 			IOException {
 		final int count = Common.normalise(req.getParameter("queries"));
-		final Random random = ThreadLocalRandom.current();
+		final CachedWorld[] worlds = new CachedWorld[count];
 
-		//TODO prevent duplicate numbers to be added
-		List<Integer> keys = new ArrayList<Integer>(count);
 		for (int i = 0; i < count; i++) {
-			keys.add(new Integer(random.nextInt(DB_ROWS) + 1));
+			worlds[i] = cache.get(ThreadLocalRandom.current().nextInt(DB_ROWS) + 1);
 		}
-		
+
 		// Set content type to JSON
 		res.setHeader(Common.HEADER_CONTENT_TYPE, Common.CONTENT_TYPE_JSON);
 
 		// Write JSON encoded message to the response.
-		Common.MAPPER.writeValue(res.getOutputStream(), cache.getAll(keys).values());
+		Common.MAPPER.writeValue(res.getOutputStream(), worlds);
 	}
-}
+}