删除问题哪里出错了

//这是servlet的代码
public class CatalogServlet extends HttpServlet {

    private CatalogDAO catalogDAO = new CatalogDAO();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        if (req.getServletPath().indexOf("/catalog/add.do")!=-1){
            CatalogEntity catalog = CatalogDAOUtils.catalogEntity(req,resp);
            catalogDAO.addCatalog(catalog);
            resp.sendRedirect("/catalog/list.do");
        } else if (req.getServletPath().indexOf("/catalog/delete.do") != -1 ){
            String sid = req.getParameter("id");
            Integer id = Integer.valueOf(sid);
            catalogDAO.deletCatalog(id);
            resp.sendRedirect("/catalog/list.do");
        } else if (req.getServletPath().indexOf("/catalog/list.do") != -1){
            CatalogEntity catalog = new CatalogEntity();
            catalog.setId(10000);
            CatalogEntity catalogEntity = catalogDAO.getCatalogEntity(catalog);
            catalog = catalogDAO.getCatalogEntity(catalog);
            req.setAttribute("catalog",catalog);
            req.getRequestDispatcher("/WEB-INF/pages/catalog/catalog_list.jsp").forward(req,resp);
        }
    }
}
//DAO类的代码
public class CatalogDAO {
    private SqlSession sqlSession ;
    private CatalogEntity catalogEntity ;


    private SqlSession getSqlSession (){
        sqlSession = SqlSessionFactoryutils.getSqlSessionFactory().openSession();
        return sqlSession;
    }


    public CatalogEntity getCatalogEntity(CatalogEntity catalog ){
        try{
           catalogEntity = getSqlSession().selectOne("selectCatalog",catalog) ;
        } catch (Exception e){
            e.printStackTrace();
        } finally {
            sqlSession.close();
        }
        return catalogEntity;
    }

    public void deletCatalog(Integer id){
        try{
            sqlSession = getSqlSession();
            sqlSession.delete("deleteCatalog",id);
        } catch (Exception e ){
            e.printStackTrace();
        } finally {
            sqlSession.close();
        }
    }

    public void addCatalog(CatalogEntity catalog){
       try{
           getSqlSession().insert("addCatalog",catalog);
       } catch (Exception e){
           e.printStackTrace();
       } finally {
           sqlSession.close();
       }
    }
}

//数据库mapper
<mapper namespace="com.imooc.entity.CatalogEntity">
    <delete id="deleteCatalog" >
        DELETE FROM catalog WHERE id = #{id}
    </delete>

    <insert id="addCatalog" useGeneratedKeys="true" keyProperty="id">
        INSERT INTO catalog (title,pid,info)
        VALUES (#{title},#{pid},#{info})
    </insert>


    <select id="selectCatalog" resultMap="forCatalog">
        SELECT * FROM catalog WHERE id = #{id}
    </select>

    <select id="selectByPid" resultMap="forCatalog">
        SELECT * FROM catalog WHERE pid = #{id}
    </select>

    <resultMap id="forCatalog" type="com.imooc.entity.CatalogEntity">
        <result column="id" property="id" ></result>
        <result column="title" property="title"></result>
        <result column="pid" property="pid"></result>
        <result column="info" property="info"></result>
        <collection property="children" column="id" select="selectByPid"></collection>
    </resultMap>
</mapper>

点击删除链接的时候要删除的catalog的id能跟着request传递，但是就是不能在数据库中删除