```python
from typing import List
from fastapi import APIRouter, Depends, HTTPException
from sqlalchemy.orm import Session

from app.db import get_db
from app.models import Post
from app.schemas import PostCreate, PostResponse

router = APIRouter()

@router.get("/posts", response_model=List[PostResponse])
def get_posts(db: Session = Depends(get_db)):
    posts = db.query(Post).all()
    return posts

@router.post("/posts", response_model=PostResponse)
def create_post(post: PostCreate, db: Session = Depends(get_db)):
    new_post = Post(**post.dict())
    db.add(new_post)
    db.commit()
    db.refresh(new_post)
    return new_post

@router.get("/posts/{post_id}", response_model=PostResponse)
def get_post(post_id: int, db: Session = Depends(get_db)):
    post = db.query(Post).filter(Post.id == post_id).first()
    if not post:
        raise HTTPException(status_code=404, detail="Post not found")
    return post

@router.put("/posts/{post_id}", response_model=PostResponse)
def update_post(post_id: int, post: PostCreate, db: Session = Depends(get_db)):
    db_post = db.query(Post).filter(Post.id == post_id).first()
    if not db_post:
        raise HTTPException(status_code=404, detail="Post not found")
    for field, value in post.dict().items():
        setattr(db_post, field, value)
    db.commit()
    db.refresh(db_post)
    return db_post

@router.delete("/posts/{post_id}", response_model=None)
def delete_post(post_id: int, db: Session = Depends(get_db)):
    post = db.query(Post).filter(Post.id == post_id).first()
    if not post:
        raise HTTPException(status_code=404, detail="Post not found")
    db.delete(post)
    db.commit()
    return
```


- `GET /posts`: Retrieve a list of all posts
- `POST /posts`: Create a new post
- `GET /posts/{post_id}`: Retrieve a specific post by ID
- `PUT /posts/{post_id}`: Update a specific post by ID
- `DELETE /posts/{post_id}`: Delete a specific post by ID

It uses the `Post` model from `app.models` and the `PostCreate` and `PostResponse` schemas from `app.schemas`. The `get_db` function from `app.db` is used to obtain a database session.

Note that you'll need to import the required models, schemas, and database dependencies in your actual application.