Controller używający EntityManager

PC27-SklepSpring/src/main/java/sklep/alternatywne_dostepy_do_bazy/ProductController_v2.java

+package sklep.alternatywne_dostepy_do_bazy;
+
+import jakarta.persistence.EntityManager;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Controller;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.ResponseBody;
+import sklep.model.Product;
+
+import java.util.List;
+
+
+@Controller
+@RequestMapping("/products_v2")
+public class ProductController_v2 {
+    @Autowired
+    private EntityManager em;
+
+    @GetMapping(produces = "text/plain;charset=UTF-8")
+    @ResponseBody
+    public String readAll() {
+        List<Product> products = em.createNamedQuery("Product.findAll", Product.class).getResultList();
+        StringBuilder sb = new StringBuilder("Lista produktów:\n");
+        for (Product product : products) {
+            sb.append(" * ")
+                    .append(product.getProductName())
+                    .append(" za cenę ")
+                    .append(product.getPrice())
+                    .append('\n');
+        }
+        return sb.toString();
+    }
+}

PC27-SklepSpring/src/main/java/sklep/controller/ProductController.java

 package sklep.controller;
 
+import jakarta.persistence.EntityManager;
+import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.ResponseBody;
+import sklep.model.Product;
+
+import java.util.List;
 
-import java.sql.*;
 
 @Controller
 @RequestMapping("/products")
 public class ProductController {
+    @Autowired
+    private EntityManager em;
 
     @GetMapping(produces = "text/plain;charset=UTF-8")
     @ResponseBody
     public String readAll() {
+        List<Product> products = em.createNamedQuery("Product.findAll", Product.class).getResultList();
         StringBuilder sb = new StringBuilder("Lista produktów:\n");
-        try(Connection c = DriverManager.getConnection("jdbc:postgresql://localhost:5432/sklep", "kurs", "abc123");
-            Statement stmt = c.createStatement();
-            ResultSet rs = stmt.executeQuery("SELECT * FROM products ORDER BY product_id")) {
-
-            while(rs.next()) {
-                sb.append("* produkt ")
-                        .append(rs.getString("product_name"))
-                        .append(" za cenę ")
-                        .append(rs.getBigDecimal("price"))
-                        .append('\n');
-            }
-        } catch (SQLException e) {
-            e.printStackTrace();
-            sb.append("Błąd: " + e);
+        for (Product product : products) {
+            sb.append(" * ")
+                    .append(product.getProductName())
+                    .append(" za cenę ")
+                    .append(product.getPrice())
+                    .append('\n');
         }
         return sb.toString();
     }