enable new Angular application

Remove the controller method that returned the VueJS index page.
Add resource handlers that redirect to the Angular application.
I added two implementations, but activated only one. At the moment I am
not sure which solution is the better. We keep both so that we can
easily switch if need arises.

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

@@ -7,10 +7,8 @@ import java.text.Collator;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.EnumSet;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
-import java.util.Map;
 import java.util.Set;
 import java.util.SortedSet;
 import java.util.TreeSet;
@@ -49,14 +47,12 @@ import org.springframework.http.ResponseEntity;
 import org.springframework.stereotype.Controller;
 import org.springframework.util.StreamUtils;
 import org.springframework.web.bind.annotation.CrossOrigin;
-import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PathVariable;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RequestMethod;
 import org.springframework.web.bind.annotation.RequestParam;
 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;
@@ -92,17 +88,6 @@ public class PdbController implements HardcodedValues, PropertyKeys {
         this.plotter = plotter;
     }
 
-    @GetMapping("/")
-    public ModelAndView index() {
-        final String view = "main";
-        final Map<String, Object> model = new HashMap<>();
-        // model.put("oldestValue",
-        // LocalDateTime.now().minusDays(7).format(DATE_FORMAT_BEGIN));
-        // model.put("latestValue", LocalDateTime.now().format(DATE_FORMAT_END));
-        model.put("isProduction", modeProduction);
-        return new ModelAndView(view, model);
-    }
-
     @RequestMapping(path = "/plots", //
             method = RequestMethod.GET, //
             consumes = MediaType.APPLICATION_JSON_VALUE, //
@@ -227,7 +212,7 @@ public class PdbController implements HardcodedValues, PropertyKeys {
     @ResponseBody
     AutocompleteResponse autocomplete(@RequestParam(name = "query") final String query,
             @RequestParam(name = "caretIndex") final int caretIndex,
-            @RequestParam(name = "resultMode", defaultValue = "CUT_AT_DOT") ResultMode resultMode) {
+            @RequestParam(name = "resultMode", defaultValue = "CUT_AT_DOT") final ResultMode resultMode) {
 
         // TODO get date range from UI
         final DateTimeRange dateRange = DateTimeRange.max();
@@ -249,12 +234,13 @@ public class PdbController implements HardcodedValues, PropertyKeys {
     }
 
     private List<Proposal> exampleProposals() {
-        List<Proposal> result = new ArrayList<Proposal>();
+        final List<Proposal> result = new ArrayList<Proposal>();
 
         if (queryExamples.length() > 0) {
             final String[] exampleQueries = queryExamples.split(Pattern.quote(";"));
-            for (String example : exampleQueries) {
-                Proposal p = new Proposal(" Example: " + example, example, true, example + " ", example.length() + 1);
+            for (final String example : exampleQueries) {
+                final Proposal p = new Proposal(" Example: " + example, example, true, example + " ",
+                        example.length() + 1);
                 result.add(p);
             }
         }

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

@@ -1,11 +1,16 @@
 package org.lucares.pdbui;
 
+import java.io.IOException;
 import java.nio.file.Paths;
 
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.core.io.Resource;
 import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
+import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
+import org.springframework.web.servlet.resource.PathResourceResolver;
 
 @Configuration
 public class WebConfiguration implements WebMvcConfigurer, HardcodedValues, PropertyKeys {
@@ -19,9 +24,65 @@ public class WebConfiguration implements WebMvcConfigurer, HardcodedValues, Prop
     @Override
     public void addResourceHandlers(final ResourceHandlerRegistry registry) {
 
+        addResourceHandlerForPlottedImages(registry);
+
+        // addResourceHandlerForAngular(registry);
+    }
+
+    private void addResourceHandlerForPlottedImages(final ResourceHandlerRegistry registry) {
         final String pathPattern = "/" + WEB_IMAGE_OUTPUT_PATH + "/**";
         final String resourceLocation = "file:" + Paths.get(outputDir).toAbsolutePath() + "/";
 
         registry.addResourceHandler(pathPattern).addResourceLocations(resourceLocation);
     }
+
+    /**
+     * This is one way to make Angular and SpringBoot play together. The other
+     * described in {@link #addViewControllers(ViewControllerRegistry)}.
+     * 
+     * @param registry
+     */
+    @SuppressWarnings("unused")
+    private void addResourceHandlerForAngular(final ResourceHandlerRegistry registry) {
+        // Redirect all to Angular for all non existing resources.
+        // This way Angular's routing & navigation (https://angular.io/guide/router) can
+        // work. Without it SpringBoot would only show 404 pages for all of Angular's
+        // pages, because the request would not even be send to Angular.
+        //
+        // Technically we are answering all requests for which SpringBoot does not find
+        // a resource with Angular's index.html. The Angular will then use its routing
+        // to determine which sub-page to show.
+        //
+        // This makes Angular also responsible for all 404 pages.
+        registry.addResourceHandler("/**").addResourceLocations("classpath:/resources/").resourceChain(true)
+                .addResolver(new PathResourceResolver() {
+                    @Override
+                    protected Resource getResource(final String resourcePath, final Resource location)
+                            throws IOException {
+                        final Resource requestedResource = location.createRelative(resourcePath);
+
+                        return requestedResource.exists() && requestedResource.isReadable() ? requestedResource
+                                : new ClassPathResource("/resources/index.html");
+                    }
+                });
+    }
+
+    /**
+     * This is one way to make Angular and SpringBoot play together. The other
+     * described in {@link #addResourceHandlerForAngular(ResourceHandlerRegistry)}
+     */
+    @Override
+    public void addViewControllers(final ViewControllerRegistry registry) {
+
+        // Redirect requests to Angular.
+        // This works by returning Angular's index.html for requests that should be
+        // handled by Angular.
+        //
+        // Using this solution SpringBoot is responsible for 404s.
+
+        registry.addViewController("/").setViewName("forward:/index.html");
+        registry.addViewController("/vis").setViewName("forward:/index.html");
+        registry.addViewController("/upload").setViewName("forward:/index.html");
+        registry.addViewController("/help").setViewName("forward:/index.html");
+    }
 }