enable client side caching for plot requests

Doesn't work perfectly yet, because the height/width sometimes changes
by one or two pixels.

pdb-ui/src/main/java/org/lucares/pdbui/PdbController.java

@@ -1,6 +1,7 @@
 package org.lucares.pdbui;
 
 import java.io.FileInputStream;
+import java.io.IOException;
 import java.io.OutputStream;
 import java.text.Collator;
 import java.util.ArrayList;
@@ -36,7 +37,9 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.http.CacheControl;
 import org.springframework.http.MediaType;
+import org.springframework.http.ResponseEntity;
 import org.springframework.stereotype.Controller;
 import org.springframework.util.StreamUtils;
 import org.springframework.web.bind.annotation.GetMapping;
@@ -49,9 +52,13 @@ import org.springframework.web.bind.annotation.ResponseBody;
 import org.springframework.web.servlet.ModelAndView;
 import org.springframework.web.servlet.mvc.method.annotation.StreamingResponseBody;
 
+import com.fasterxml.jackson.core.JsonParseException;
+import com.fasterxml.jackson.databind.JsonMappingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
 @Controller
 @EnableAutoConfiguration
-public class PdbController implements HardcodedValues {
+public class PdbController implements HardcodedValues, PropertyKeys {
 
 	private static final Logger LOGGER = LoggerFactory.getLogger(PdbController.class);
 
@@ -60,9 +67,12 @@ public class PdbController implements HardcodedValues {
 
 	private final ReentrantLock plotterLock = new ReentrantLock();
 
-	@Value("${mode.production:true}")
+	@Value("${" + PRODUCTION_MODE + ":true}")
 	private boolean modeProduction;
 
+	@Value("${" + CACHE_IMAGES_DURATION_SECONDS + ":" + CACHE_IMAGES_DURATION_SECONDS_DEFAULT + "}")
+	private int cacheDurationInSeconds;
+
 	public PdbController(final PerformanceDb db, final Plotter plotter) {
 		this.db = db;
 		this.plotter = plotter;
@@ -79,13 +89,29 @@ public class PdbController implements HardcodedValues {
 		return new ModelAndView(view, model);
 	}
 
+	@RequestMapping(path = "/plots", //
+			method = RequestMethod.GET, //
+			consumes = MediaType.APPLICATION_JSON_UTF8_VALUE, //
+			produces = MediaType.APPLICATION_JSON_UTF8_VALUE //
+	)
+	@ResponseBody
+	ResponseEntity<PlotResponse> createPlotGet(@RequestParam(name = "request") final String request)
+			throws InternalPlottingException, InterruptedException, JsonParseException, JsonMappingException,
+			IOException {
+
+		final ObjectMapper objectMapper = new ObjectMapper();
+		final PlotRequest plotRequest = objectMapper.readValue(request, PlotRequest.class);
+
+		return createPlot(plotRequest);
+	}
+
 	@RequestMapping(path = "/plots", //
 			method = RequestMethod.POST, //
 			consumes = MediaType.APPLICATION_JSON_UTF8_VALUE, //
 			produces = MediaType.APPLICATION_JSON_UTF8_VALUE //
 	)
 	@ResponseBody
-	PlotResponse createPlot(@RequestBody final PlotRequest request)
+	ResponseEntity<PlotResponse> createPlot(@RequestBody final PlotRequest request)
 			throws InternalPlottingException, InterruptedException {
 
 		final PlotSettings plotSettings = PlotSettingsTransformer.toSettings(request);
@@ -107,7 +133,11 @@ public class PdbController implements HardcodedValues {
 						: imageUrl;
 
 				final PlotResponseStats stats = PlotResponseStats.fromDataSeries(result.getDataSeries());
-				return new PlotResponse(stats, imageUrl, thumbnailUrl);
+				final PlotResponse plotResponse = new PlotResponse(stats, imageUrl, thumbnailUrl);
+
+				final CacheControl cacheControl = CacheControl.maxAge(cacheDurationInSeconds, TimeUnit.SECONDS);
+
+				return ResponseEntity.ok().cacheControl(cacheControl).body(plotResponse);
 			} catch (final NoDataPointsException e) {
 				throw new NotFoundException(e);
 			} finally {

pdb-ui/src/main/java/org/lucares/pdbui/PropertyKeys.java

@@ -11,4 +11,20 @@ public interface PropertyKeys {
 	 * Path for temporary files
 	 */
 	String TMP_DIR = "path.tmp";
+
+	/**
+	 * The number of seconds generated images shall be cached.
+	 */
+	String CACHE_IMAGES_DURATION_SECONDS = "cache.images.duration.seconds";
+
+	/**
+	 * Default value for {@link PropertyKeys#CACHE_IMAGES_DURATION_SECONDS}
+	 */
+	String CACHE_IMAGES_DURATION_SECONDS_DEFAULT = "3600";
+
+	/**
+	 * Indicates whether or not this instance is running in production. This
+	 * property is used to switch Vue.js into production or development mode.
+	 */
+	String PRODUCTION_MODE = "mode.production";
 }

pdb-ui/src/main/java/org/lucares/pdbui/WebConfiguration.java

@@ -1,19 +1,25 @@
 package org.lucares.pdbui;
 
 import java.nio.file.Paths;
+import java.util.concurrent.TimeUnit;
 
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.http.CacheControl;
 import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
-import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
+import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
 
 @Configuration
-public class WebConfiguration extends WebMvcConfigurerAdapter implements HardcodedValues, PropertyKeys {
+public class WebConfiguration implements WebMvcConfigurer, HardcodedValues, PropertyKeys {
 
 	private final String outputDir;
+	private final int cacheDurationInSeconds;
 
-	public WebConfiguration(@Value("${" + PATH_GENERATED_IMAGES + "}") final String outputDir) {
+	public WebConfiguration(@Value("${" + PATH_GENERATED_IMAGES + "}") final String outputDir,
+			@Value("${" + CACHE_IMAGES_DURATION_SECONDS + ":" + CACHE_IMAGES_DURATION_SECONDS_DEFAULT
+					+ "}") final int cacheDurationInSeconds) {
 		this.outputDir = outputDir;
+		this.cacheDurationInSeconds = cacheDurationInSeconds;
 	}
 
 	@Override
@@ -22,6 +28,7 @@ public class WebConfiguration extends WebMvcConfigurerAdapter implements Hardcod
 		final String pathPattern = "/" + WEB_IMAGE_OUTPUT_PATH + "/**";
 		final String resourceLocation = "file:" + Paths.get(outputDir).toAbsolutePath() + "/";
 
-		registry.addResourceHandler(pathPattern).addResourceLocations(resourceLocation);
+		final CacheControl cacheControl = CacheControl.maxAge(cacheDurationInSeconds, TimeUnit.SECONDS);
+		registry.addResourceHandler(pathPattern).addResourceLocations(resourceLocation).setCacheControl(cacheControl);
 	}
 }

pdb-ui/src/main/resources/application.properties

@@ -4,4 +4,6 @@ db.base=${base.dir}/db
 path.tmp=${base.dir}/tmp
 path.output=${base.dir}/out
 
+cache.images.duration.seconds=3600
+
 logging.config=classpath:log4j2.xml

pdb-ui/src/main/resources/resources/js/ui.js

@@ -908,7 +908,10 @@ function sendPlotRequest(query){
 	};
 	
 	data.searchBar.imagelink = '';
-	postJson("plots", request, success, error);
+	const requestParam = {
+		'request': JSON.stringify(request)
+	};
+	getJson("plots", requestParam, success, error)
 }
 
 function updateImageLink(query) {
@@ -1002,7 +1005,10 @@ function createDashboardItem(originalQuery, field, imageHeight, imageWidth)
 			data.dashboard.progress.value++;
 			createDashboardItem(originalQuery, field, imageHeight, imageWidth);
 		};
-		postJson("plots", request, success, error);
+		var requestParam = {
+			request: JSON.stringify(request)
+		};
+		getJson("plots", requestParam, success, error)
 	}
 }
 
@@ -1045,7 +1051,8 @@ function getJson(url, requestData, successCallback, errorCallback) {
 			type: "GET",
 			url: url,
 			data: requestData,
-			contentType: 'application/json'
+			contentType: 'application/json',
+			cache:true
 		})
 		.done(successCallback)
 		.fail(errorCallback);