Try to add FilterService.java

src/main/java/site/easystartup/easystartupcore/controller/ForumController.java

@@ -1,22 +1,36 @@
 package site.easystartup.easystartupcore.controller;
 
+import com.google.common.collect.Lists;
 import lombok.RequiredArgsConstructor;
 import lombok.val;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Controller;
 import org.springframework.ui.Model;
 import org.springframework.web.bind.annotation.GetMapping;
+import site.easystartup.easystartupcore.domain.forum.Discussion;
+import site.easystartup.easystartupcore.domain.forum.Topic;
 import site.easystartup.easystartupcore.repos.forum.TopicRepo;
 
+import java.util.Collections;
+
 @Controller
 @RequiredArgsConstructor(onConstructor_ = @Autowired)
 public class ForumController {
     private final TopicRepo topicRepo;
 
+    private final Discussion discussion;
+
     @GetMapping("/forum")
     public String forumMain(Model model) {
         val topic = topicRepo.findAll();
         model.addAttribute("topics", topic);
         return "forum";
     }
+
+    @GetMapping("/forum/my")
+    public String forumMy(Model model) {
+        val topic = Lists.newArrayList(topicRepo.findAll());
+        model.addAttribute("topics", topic);
+        return "forum";
+    }
 }

src/main/java/site/easystartup/easystartupcore/domain/forum/Topic.java

@@ -20,6 +20,7 @@ public class Topic {
     @GeneratedValue(strategy = GenerationType.AUTO)
     private long id;
     private String title;
+    private String author;
     private int size;
     private String description;
     private Date last_update;

src/main/java/site/easystartup/easystartupcore/filter/FilterService.java

@@ -0,0 +1,14 @@
+package site.easystartup.easystartupcore.filter;
+
+import site.easystartup.easystartupcore.domain.forum.Discussion;
+import site.easystartup.easystartupcore.domain.forum.DiscussionMessage;
+
+import java.util.List;
+
+public interface FilterService {
+    List<DiscussionMessage> getMessagesByDiscussionId(long discussionId);
+
+    List<Discussion> getDiscussionByAuthor(String author);
+
+    List<Discussion> getDiscussionByMember(String member);
+}

src/main/java/site/easystartup/easystartupcore/filter/StreamFilterService.java

@@ -0,0 +1,31 @@
+package site.easystartup.easystartupcore.filter;
+
+import com.google.common.collect.Lists;
+import lombok.RequiredArgsConstructor;
+import org.springframework.beans.factory.annotation.Autowired;
+import site.easystartup.easystartupcore.domain.forum.Discussion;
+import site.easystartup.easystartupcore.domain.forum.DiscussionMessage;
+import site.easystartup.easystartupcore.repos.forum.DiscussionMessageRepo;
+
+import java.util.List;
+
+@RequiredArgsConstructor(onConstructor_ = @Autowired)
+public class StreamFilterService implements FilterService {
+    private final DiscussionMessageRepo discussionMessageRepo;
+
+    @Override
+    public List<DiscussionMessage> getMessagesByDiscussionId(long discussionId) {
+        //Lists.newArrayList(discussionMessageRepo.findAll()).stream().filter()
+        return null;
+    }
+
+    @Override
+    public List<Discussion> getDiscussionByAuthor(String author) {
+        return null;
+    }
+
+    @Override
+    public List<Discussion> getDiscussionByMember(String member) {
+        return null;
+    }
+}