pagination work

spring-security-rest-full/src/main/java/org/baeldung/web/controller/FooController.java

@@ -9,6 +9,7 @@ import javax.servlet.http.HttpServletResponse;
 import org.baeldung.persistence.model.Foo;
 import org.baeldung.persistence.service.IFooService;
 import org.baeldung.web.exception.MyResourceNotFoundException;
+import org.baeldung.web.hateoas.PaginatedResultsRetrievedEvent;
 import org.baeldung.web.util.LinkUtil;
 import org.baeldung.web.util.ResourceCreated;
 import org.baeldung.web.util.RestPreconditions;
@@ -72,7 +73,7 @@ public class FooController {
         if (page > resultPage.getTotalPages()) {
             throw new MyResourceNotFoundException();
         }
-        // eventPublisher.publishEvent(new PaginatedResultsRetrievedEvent<Foo>(Foo.class, uriBuilder, response, page, resultPage.getTotalPages(), size));
+        eventPublisher.publishEvent(new PaginatedResultsRetrievedEvent<Foo>(Foo.class, uriBuilder, response, page, resultPage.getTotalPages(), size));
 
         return resultPage.getContent();
     }

spring-security-rest-full/src/main/java/org/baeldung/web/hateoas/PaginatedResultsRetrievedDiscoverabilityListener.java

@@ -0,0 +1,107 @@
+package org.baeldung.web.hateoas;
+
+import javax.servlet.http.HttpServletResponse;
+
+import org.baeldung.web.util.LinkUtil;
+import org.springframework.context.ApplicationListener;
+import org.springframework.stereotype.Component;
+import org.springframework.web.util.UriComponentsBuilder;
+
+import com.google.common.base.Preconditions;
+import com.google.common.net.HttpHeaders;
+
+@SuppressWarnings({ "rawtypes" })
+@Component
+class PaginatedResultsRetrievedDiscoverabilityListener implements ApplicationListener<PaginatedResultsRetrievedEvent> {
+
+    private static final String PAGE = "page";
+
+    public PaginatedResultsRetrievedDiscoverabilityListener() {
+        super();
+    }
+
+    // API
+
+    @Override
+    public final void onApplicationEvent(final PaginatedResultsRetrievedEvent ev) {
+        Preconditions.checkNotNull(ev);
+
+        addLinkHeaderOnPagedResourceRetrieval(ev.getUriBuilder(), ev.getResponse(), ev.getClazz(), ev.getPage(), ev.getTotalPages(), ev.getPageSize());
+    }
+
+    // - note: at this point, the URI is transformed into plural (added `s`) in a hardcoded way - this will change in the future
+    final void addLinkHeaderOnPagedResourceRetrieval(final UriComponentsBuilder uriBuilder, final HttpServletResponse response, final Class clazz, final int page, final int totalPages, final int pageSize) {
+        plural(uriBuilder, clazz);
+
+        final StringBuilder linkHeader = new StringBuilder();
+        if (hasNextPage(page, totalPages)) {
+            final String uriForNextPage = constructNextPageUri(uriBuilder, page, pageSize);
+            linkHeader.append(LinkUtil.createLinkHeader(uriForNextPage, LinkUtil.REL_NEXT));
+        }
+        if (hasPreviousPage(page)) {
+            final String uriForPrevPage = constructPrevPageUri(uriBuilder, page, pageSize);
+            appendCommaIfNecessary(linkHeader);
+            linkHeader.append(LinkUtil.createLinkHeader(uriForPrevPage, LinkUtil.REL_PREV));
+        }
+        if (hasFirstPage(page)) {
+            final String uriForFirstPage = constructFirstPageUri(uriBuilder, pageSize);
+            appendCommaIfNecessary(linkHeader);
+            linkHeader.append(LinkUtil.createLinkHeader(uriForFirstPage, LinkUtil.REL_FIRST));
+        }
+        if (hasLastPage(page, totalPages)) {
+            final String uriForLastPage = constructLastPageUri(uriBuilder, totalPages, pageSize);
+            appendCommaIfNecessary(linkHeader);
+            linkHeader.append(LinkUtil.createLinkHeader(uriForLastPage, LinkUtil.REL_LAST));
+        }
+
+        if (linkHeader.length() > 0) {
+            response.addHeader(HttpHeaders.LINK, linkHeader.toString());
+        }
+    }
+
+    final String constructNextPageUri(final UriComponentsBuilder uriBuilder, final int page, final int size) {
+        return uriBuilder.replaceQueryParam(PAGE, page + 1).replaceQueryParam("size", size).build().encode().toUriString();
+    }
+
+    final String constructPrevPageUri(final UriComponentsBuilder uriBuilder, final int page, final int size) {
+        return uriBuilder.replaceQueryParam(PAGE, page - 1).replaceQueryParam("size", size).build().encode().toUriString();
+    }
+
+    final String constructFirstPageUri(final UriComponentsBuilder uriBuilder, final int size) {
+        return uriBuilder.replaceQueryParam(PAGE, 0).replaceQueryParam("size", size).build().encode().toUriString();
+    }
+
+    final String constructLastPageUri(final UriComponentsBuilder uriBuilder, final int totalPages, final int size) {
+        return uriBuilder.replaceQueryParam(PAGE, totalPages).replaceQueryParam("size", size).build().encode().toUriString();
+    }
+
+    final boolean hasNextPage(final int page, final int totalPages) {
+        return page < totalPages - 1;
+    }
+
+    final boolean hasPreviousPage(final int page) {
+        return page > 0;
+    }
+
+    final boolean hasFirstPage(final int page) {
+        return hasPreviousPage(page);
+    }
+
+    final boolean hasLastPage(final int page, final int totalPages) {
+        return totalPages > 1 && hasNextPage(page, totalPages);
+    }
+
+    final void appendCommaIfNecessary(final StringBuilder linkHeader) {
+        if (linkHeader.length() > 0) {
+            linkHeader.append(", ");
+        }
+    }
+
+    // template
+
+    protected void plural(final UriComponentsBuilder uriBuilder, final Class clazz) {
+        final String resourceName = clazz.getSimpleName() + "s";
+        uriBuilder.path("/" + resourceName);
+    }
+
+}

spring-security-rest-full/src/main/java/org/baeldung/web/hateoas/PaginatedResultsRetrievedEvent.java

@@ -0,0 +1,67 @@
+package org.baeldung.web.hateoas;
+
+import java.io.Serializable;
+
+import javax.servlet.http.HttpServletResponse;
+
+import org.springframework.context.ApplicationEvent;
+import org.springframework.web.util.UriComponentsBuilder;
+
+/**
+ * Event that is fired when a paginated search is performed.
+ * <p/>
+ * This event object contains all the information needed to create the URL for the paginated results
+ * 
+ * @param <T>
+ *            Type of the result that is being handled (commonly Entities).
+ */
+public final class PaginatedResultsRetrievedEvent<T extends Serializable> extends ApplicationEvent {
+    private final UriComponentsBuilder uriBuilder;
+    private final HttpServletResponse response;
+    private final int page;
+    private final int totalPages;
+    private final int pageSize;
+
+    public PaginatedResultsRetrievedEvent(final Class<T> clazz, final UriComponentsBuilder uriBuilderToSet, final HttpServletResponse responseToSet, final int pageToSet, final int totalPagesToSet, final int pageSizeToSet) {
+        super(clazz);
+
+        uriBuilder = uriBuilderToSet;
+        response = responseToSet;
+        page = pageToSet;
+        totalPages = totalPagesToSet;
+        pageSize = pageSizeToSet;
+    }
+
+    // API
+
+    public final UriComponentsBuilder getUriBuilder() {
+        return uriBuilder;
+    }
+
+    public final HttpServletResponse getResponse() {
+        return response;
+    }
+
+    public final int getPage() {
+        return page;
+    }
+
+    public final int getTotalPages() {
+        return totalPages;
+    }
+
+    public final int getPageSize() {
+        return pageSize;
+    }
+
+    /**
+     * The object on which the Event initially occurred.
+     * 
+     * @return The object on which the Event initially occurred.
+     */
+    @SuppressWarnings("unchecked")
+    public final Class<T> getClazz() {
+        return (Class<T>) getSource();
+    }
+
+}

spring-security-rest-full/src/main/java/org/baeldung/web/util/LinkUtil.java

@@ -7,6 +7,12 @@ import javax.servlet.http.HttpServletResponse;
  */
 public final class LinkUtil {
 
+    public static final String REL_COLLECTION = "collection";
+    public static final String REL_NEXT = "next";
+    public static final String REL_PREV = "prev";
+    public static final String REL_FIRST = "first";
+    public static final String REL_LAST = "last";
+
     private LinkUtil() {
         throw new AssertionError();
     }