edit book servlet now interacts with database

src/main/java/de/hsel/itech/db/Database.java

@@ -146,6 +146,28 @@ public class Database {
         return author;
     }
 
+    @Nullable
+    public Author getAuthor(String name) {
+        Author author = null;
+
+        Map.Entry<List<ResultSet>, Connection> set = getResultSets(this.author, "name", name);
+
+        if(set == null){
+            return null;
+        }
+
+        if (set.getKey().size() > 0) {
+            try {
+                author = new Author(set.getKey().get(0).getLong("id"), set.getKey().get(0).getString("name"));
+            } catch (SQLException e) {
+                e.printStackTrace();
+            }
+        }
+
+
+        return author;
+    }
+
     /**
      * gets category by id.
      *
@@ -562,6 +584,32 @@ public class Database {
         return null;
     }
 
+    /**
+     * gets specific entries from table.
+     *
+     * @param table  table name
+     * @param column column to match
+     * @return {@link java.util.Map.Entry}
+     */
+    @Nullable
+    private Map.Entry<List<ResultSet>, Connection> getResultSets(@NotNull String table, @NotNull String column, @NotNull String value) {
+        Connection connection = getConnection();
+        try {
+            assert connection != null;
+            PreparedStatement statement = connection.prepareStatement("SELECT * FROM ? WHERE ? = ?");
+            statement.setString(1, table);
+            statement.setString(2, column);
+            statement.setString(3, value);
+
+            System.out.println(statement);
+
+            return getAllEntries(connection, statement);
+        } catch (SQLException ex) {
+            ex.printStackTrace();
+        }
+        return null;
+    }
+
     /**
      * gets all specified columns from table.
      *

src/main/java/de/hsel/itech/servlet/AddBook.java

@@ -1,13 +1,10 @@
 package de.hsel.itech.servlet;
 
-import de.hsel.itech.db.pojo.Book;
-
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import java.io.IOException;
 import java.io.PrintWriter;
-import java.util.ArrayList;
 
 public class AddBook extends HttpServlet {
 
@@ -20,7 +17,7 @@ public class AddBook extends HttpServlet {
 
         Utillity.insertFile(out, "template_head.html");
         de.hsel.itech.db.Database db = de.hsel.itech.db.Database.getInstance();
-        ArrayList<Book> books = db.getBooks();
+        //List<Book> books = db.getBooks();
 
         out.println("<form class=\"m-container\" action=\"booklist\" method=post>");
         Utillity.addInput(out,"Titel", "title");
@@ -29,6 +26,7 @@ public class AddBook extends HttpServlet {
         Utillity.addInput(out,"Jahr", "year", "2019");
         Utillity.addInput(out,"Beschreibung", "description");
         Utillity.addInput(out,"Verlag", "publisher");
+        Utillity.addInput(out,"Kategorie", "category");
         Utillity.addInput(out,"Bild", "image", "DxAzOKSiPoE");
         Utillity.addTypeButton(out, "Hinzufügen", "submit");
         out.println("</form>");

src/main/java/de/hsel/itech/servlet/BookList.java

@@ -13,7 +13,7 @@ import java.io.PrintWriter;
 import java.time.Year;
 import java.util.ArrayList;
 import java.util.Enumeration;
-import java.util.Random;
+import java.util.List;
 
 public class BookList extends HttpServlet {
 
@@ -34,13 +34,13 @@ public class BookList extends HttpServlet {
         String param = req.getParameter("removeid");
         if(param != null){
             long isbn = Long.parseLong(param);
-            db.removeBook(isbn);
+            db.deleteBook(isbn);
             resp.sendRedirect("booklist");
         }
 
         if(req.getParameter("title") != null){
             String title = req.getParameter("title");
-            String author = req.getParameter("author");
+            String authorName = req.getParameter("author");
             int price = Integer.parseInt(req.getParameter("price"));
             int year = Integer.parseInt(req.getParameter("year"));
             String category = req.getParameter("category");
@@ -48,14 +48,24 @@ public class BookList extends HttpServlet {
             String publisher = req.getParameter("publisher");
             String image = req.getParameter("image");
 
+
+            ArrayList<Author> authors = new ArrayList<Author>();
+            Author author = null;
+
+            author = db.getAuthor(authorName);
+
+            if(author == null){
+                author = new Author(authorName);
+                db.insert(author);
+            }
+            authors.add(author);
             Book book = new Book(
-                    new Random().nextInt(),
+                    authors,
-                    new Author(0,author),
+                    new Publisher(publisher),
-                    new Publisher(0,publisher),
+                    new Category(category, "DxAzOKSiPoE"),
-                    new Category(0,category, "DxAzOKSiPoE"),
                     title, Year.of(year),price,description, image
             );
-            db.addBook(book);
+            db.insert(book);
 
             resp.sendRedirect("booklist");
         }
@@ -67,7 +77,9 @@ public class BookList extends HttpServlet {
         Utillity.insertFile(out, "template_head.html");
 
 
-        ArrayList<Book> books = db.getBooks();
+        List<Book> books = db.getBooks();
+
+        if(books != null) {
 
             //book entries
             out.println("<div class=\"m-container\">");
@@ -82,13 +94,15 @@ public class BookList extends HttpServlet {
                 out.println("  <div class=\"m-col-l-4\">");
                 out.println("<h1>" + book.getTitle() + "</h1>");
                 out.println("   <br>");
-            out.println("   <h2>" + book.getAuthor().getName() + "</h2>");
+                for (int i = 0; i < book.getAuthors().size(); i++) {
+                    out.println("   <h2>" + book.getAuthors().get(0).getName() + "</h2>");
+                }
                 out.println("   <br>");
                 out.print("   <h3>" + book.getPrice() / 100 + ",");
-            if(book.getPrice() % 100 < 10){
+                if (book.getPrice() % 100 < 10) {
                     out.print("0");
                 }
-            out.println(book.getPrice() % 100 +" &euro;</h3>");
+                out.println(book.getPrice() % 100 + " &euro;</h3>");
                 out.println("   <br>");
                 out.println("  </div>");
 
@@ -104,7 +118,7 @@ public class BookList extends HttpServlet {
                 out.println("  </div>");
             }
             out.println("</div>");
-
+        }
 
         //add book button
         Utillity.addButton(out,"Neues Buch Hinzufügen", "addbook");