Добавил репозиторий, реализовал добавление, вывод и фильтрацию сообщений.

https://www.youtube.com/watch?v=nyFLX3q3poY&list=PLU2ftbIeotGoGSEUf54LQH-DgiQPF2XRO&index=3

compose.yml

@@ -0,0 +1,10 @@
+services:
+  postgres:
+    restart: on-failure
+    image: postgres:13
+    ports:
+      - "5454:5432"
+    environment:
+      POSTGRES_USER: user
+      POSTGRES_PASSWORD: 123456
+      POSTGRES_DB: sweater_db

pom.xml

@@ -43,6 +43,22 @@
             <artifactId>spring-boot-starter-test</artifactId>
             <scope>test</scope>
         </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-data-jpa</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-docker-compose</artifactId>
+            <scope>runtime</scope>
+            <optional>true</optional>
+        </dependency>
+        <dependency>
+            <groupId>org.postgresql</groupId>
+            <artifactId>postgresql</artifactId>
+            <scope>runtime</scope>
+        </dependency>
     </dependencies>
 
     <build>

src/main/java/net/sytes/kashey/sweater/GreetingController.java

@@ -1,7 +1,10 @@
 package net.sytes.kashey.sweater;
 
+import net.sytes.kashey.sweater.domain.Message;
+import net.sytes.kashey.sweater.repository.MessageRepository;
 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestParam;
 
 import java.util.Map;
@@ -9,6 +12,12 @@ import java.util.Map;
 @Controller
 public class GreetingController {
 
+    private final MessageRepository messageRepository;
+
+    public GreetingController(MessageRepository messageRepository) {
+        this.messageRepository = messageRepository;
+    }
+
     @GetMapping("/greeting")
     public String greeting(@RequestParam(name = "name", required = false, defaultValue = "World") String name,
                            Map<String, Object> model) {
@@ -16,9 +25,29 @@ public class GreetingController {
         return "greeting";
     }
 
-    @GetMapping()
-    public String root(Map<String, Object> model) {
-        model.put("some", "Hello from main!!!");
+    @GetMapping
+    public String findAllMessages(Map<String, Object> model) {
+
+        model.put("messages", messageRepository.findAll());
+        return "main";
+    }
+
+    @PostMapping
+    public String addMessage(@RequestParam String text, @RequestParam String tag, Map<String, Object> model) {
+
+        messageRepository.save(new Message(text, tag));
+        model.put("messages", messageRepository.findAll());
+        return "main";
+    }
+
+    @PostMapping("filter")
+    public String filterByTag(@RequestParam String tag, Map<String, Object> model) {
+
+        if (tag == null || tag.isEmpty()) {
+            model.put("messages", messageRepository.findAll());
+        } else {
+            model.put("messages", messageRepository.findByTag(tag));
+        }
         return "main";
     }
 }

src/main/java/net/sytes/kashey/sweater/domain/Message.java

@@ -0,0 +1,47 @@
+package net.sytes.kashey.sweater.domain;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.GeneratedValue;
+import jakarta.persistence.GenerationType;
+import jakarta.persistence.Id;
+
+@Entity
+public class Message {
+    @Id
+    @GeneratedValue(strategy= GenerationType.AUTO)
+    private Integer id;
+    private String text;
+    private String tag;
+
+    public Message() {
+    }
+
+    public Message(String text, String tag) {
+        this.text = text;
+        this.tag = tag;
+    }
+
+    public Integer getId() {
+        return id;
+    }
+
+    public void setId(Integer id) {
+        this.id = id;
+    }
+
+    public String getText() {
+        return text;
+    }
+
+    public void setText(String text) {
+        this.text = text;
+    }
+
+    public String getTag() {
+        return tag;
+    }
+
+    public void setTag(String tag) {
+        this.tag = tag;
+    }
+}

src/main/java/net/sytes/kashey/sweater/repository/MessageRepository.java

@@ -0,0 +1,10 @@
+package net.sytes.kashey.sweater.repository;
+
+import net.sytes.kashey.sweater.domain.Message;
+import org.springframework.data.repository.CrudRepository;
+
+import java.util.List;
+
+public interface MessageRepository extends CrudRepository<Message, Integer> {
+     List<Message> findByTag(String tag);
+}

src/main/resources/application.properties

@@ -0,0 +1,6 @@
+spring.jpa.hibernate.ddl-auto = update
+spring.datasource.url=jdbc:postgresql://localhost:5454/sweater_db
+spring.datasource.username=user
+spring.datasource.password=123456
+spring.datasource.driver-class-name=org.postgresql.Driver
+spring.jpa.show-sql: true

src/main/resources/templates/main.mustache

@@ -1,5 +1,29 @@
 <html>
 <body>
-<div>{{some}}<div>
+<div>
+<form method="post">
+<input type="text" name="text" placeholder="Enter message"> </input>
+<input type="text" name="tag" placeholder="tag"></input>
+<button type="submit">Add message</button>
+</form>
+</div
+<div>
+<form method="post" action="filter">
+Tag to filer
+<br>
+   <input type="text" name="tag">
+   <button>Find</button>
+</form>
+</div>
+
+ <div>Messages list</div>
+    {{#messages}}
+    <div>
+        <b>{{id}}</b>
+        <span>{{text}}</span>
+        <i>{{tag}}</i>
+    </div>
+    {{/messages}}
+
 </body>
 </html>