Education background management system: query course list information

Posted by suz_1234 on Fri, 29 Oct 2021 11:34:01 +0200

1 demand analysis

What data should be displayed for page analysis





2 write code

2.1 preparation of Dao layer

  1. Modify CourseDao and add findCourseList method

Interface CourseDao
    //Query course list information
    public List<Course> findCourseList();

Implementation class CourseDaoImpl
    public List<Course> findCourseList() {

        try {
            //1.establish QueryRunner
            QueryRunner qr = new QueryRunner(DruidUtils.getDataSource());

            // write SQL
       String sql = "SELECT id,course_name,price,sort_num,STATUS FROM course where id_del =  ?";

            //3.Execute query
          List<Course> courseList = qr.query(sql, new BeanListHandler<Course>(Course.class), 0);

            return courseList;

        } catch (SQLException e) {
            return null;


Logical deletion

  • The essence of logical deletion is modification. The so-called logical deletion is not a real deletion, but a corresponding deletion flag in the table to modify.

  • For example, 0 is undeleted and 1 is deleted. Logically, the data is deleted, but the data itself still exists in the library.



Physical deletion

  • Physical deletion is the real deletion from the database


2.2 preparation of service layer

Modify CourseService and add findCourseList method

Interface CourseService 
    public List<Course> findCourseList();

Implementation class CourseServiceImpl
    //establish CourseDao
    CourseDao courseDao = new CourseDaoImpl();

    public List<Course> findCourseList() {

        //call Dao Make a query
        return courseDao.findCourseList();


2.3 Servlet writing

2.3.1 interface development specification

What we are doing is a front-end and back-end separation project that needs to be docked through interface documents. Therefore, during the development process, we should carefully check the api interfaces and parameter fields required by the front end

In order to develop in strict accordance with the interface and improve efficiency, the request and response formats are standardized.


Development specification


1. When making a get request, the request is made in the format of key/value, which can be obtained in the Servlet using getParameter().
2. There are three data formats for post requests. The first is Json data, which is parsed by fastjson in a jsonl type data Servlet. The second is to submit form data. The third is multipart / form data such as files
3. The unified format of response results is json

Why use JSON?

The data format is relatively simple and easy to read and write. JSON format can be used directly for server-side code, which greatly simplifies the amount of code development on server-side and client-side, but the completed tasks remain unchanged and easy to maintain



The JSON parsing tool used in this project is Alibaba's fastjson, maven project. Just import the following dependencies




2.3.2 interface documents

The front-end development is based on the interface written by the server. If the front-end personnel wait for the server personnel to complete the interface development before developing the front-end content, this is very inefficient,

Therefore, when the interface definition is completed, the tool can be used to generate the interface document, and the front-end personnel can view the interface document for front-end development. In this way, the front-end and service personnel can develop in parallel, which greatly improves the production efficiency


2.3.3 writing CourseServlet

In the CourseServlet, add the findCourseList method

public class CourseServlet extends BaseServlet {

    //Query course information list
    public void findCourseList(HttpServletRequest request, HttpServletResponse response){

        try {
            //1.Receive parameters

            //2.Business processing
            CourseService cs = new CourseServiceImpl();
            List<Course> courseList = cs.findCourseList();

            //3.Response results
            //SimplePropertyPreFilter Specify the to convert JSON field
            SimplePropertyPreFilter filter = new SimplePropertyPreFilter(Course.class,

            String result = JSON.toJSONString(courseList,filter);

        } catch (IOException e) {