增加文件前缀和后缀的设置，修缮部分代码规范

src/main/java/com/fjy/spring/service/HomeworkService.java

@@ -2,13 +2,13 @@ package com.fjy.spring.service;
 
 import com.fjy.spring.domain.Homework;
 import com.fjy.spring.domain.VHomework;
-import com.fjy.spring.domain.VWorkDetail;
 import com.fjy.spring.repository.HomeworkRepository;
 import com.fjy.spring.repository.VHomeworkRepository;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
 
 import java.util.List;
+import java.util.Optional;
 
 @Service
 public class HomeworkService {
@@ -25,4 +25,12 @@ public class HomeworkService {
     public List<VHomework> findAllVHomework(){
         return vHomeworkRepository.findAll();
     }
+
+    public Homework findById(Integer id){
+        Optional<Homework> homework = homeworkRepository.findById(id);
+        if (homework.isPresent()){
+            return (Homework)homework.get();
+        }
+        return null;
+    }
 }