2022 summer vacation software innovation laboratory training project practice 1

Class learning system

Database creation

First , We must realize that database is the foundation of application development , Without that foundation , There are many things we can't complete , For example, some of the projects UI Design （ Forms, etc ）、 Code writing and so on . If this project is developed by individuals, it may not be very troublesome , Because if the database needs to be modified during development , You can modify it by yourself slowly , from UI To code writing （ But if you are in the late stage of development , It is found that the database needs to be modified , That's a high probability ）. however , Let's think about it from another angle , If you are a team developer , Each person is responsible for a module , Suppose that each module needs to be coded based on the database , So if in the development , It is found that the database needs to be modified , It is also a very time-consuming and labor-intensive thing for the team , It can lead to a lot of serious problems , Such as code rewriting .

The users of this project are students , Students can use this website to join study groups , Then students can speak and discuss in the study group , Users can also use the existing website to log in and register accounts that do not exist .

So before the formal coding of the project , First, let's build a database

Hereby explain , The database may also need to be modified later , Because problems always appear , Here is also the process

1. First , It is necessary to analyze users , Here we will simply give the key fields of users , user ID、 user name 、 User password 、 User creation time （ You can improve the database fields by yourself ）.

   

2. Then there are students , Student information needs student number 、 full name 、QQ、 Phone number 、 Authority level （ You can improve the database fields by yourself ）

   

3. You also need a data sheet for the study group , Study groups need groups ID、 Team leader ID、 The number of team 、 Team name 、 Group Introduction 、 Among them, the group ID Primary key .

   

4. Because it can be discussed among users , We need to use database to store the content discussed here , The required field content has comments ID Number 、 The user who commented ID、 Comment on your study group 、 Comment content 、 Comment on time .

   

So far , We have created the database of the class learning system （ Very, very simple ）, Convert the model we just built into a database , Here's the picture .

after , We have successfully imported the newly created database .

Create project

After we create the database , You need to create a good project , And layer the project . Use IDEA Enterprise edition to create Web project .

First , We need to configure the database in the project , Because of this Web The project will definitely use JDBC To interact with the underlying database , For example, the user login will access the database to query whether the current user exists , When registering an account, we will use the database to add users .

Configuration database

stay WEB-ING establish lib Catalog , Import the driver of the database under this directory jar package （ Namely JDBC That set of operation ）

Above resources Create database connection profile db.properties

driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/study?&useSSL=false&serverTimezone=UTC
username=root
password=123456

Then if you remember JDBC Students of operation should also know the time of database operation , There is a database operation tool class , Namely JDBCUtil, First we need to create a util File to store our customized tool classes

public class JDBCUtil {
    
    private static final String driver;
    private static final String url;
    private static final String userName;
    private static final String password;

    static {
    
        InputStream is = JDBCUtil.class.getClassLoader().getResourceAsStream("db.properties");
        Properties properties = new Properties();
        try {
    

            properties.load(is);
        } catch (IOException e) {
    
            e.printStackTrace();
        }
        driver = properties.getProperty("driver");
        url = properties.getProperty("url");
        userName = properties.getProperty("username");
        password = properties.getProperty("password");
    }

    //  Get database connection 
    public static Connection getConnection() {
    
        Connection con = null;
        try {
    
            Class.forName(driver);
            con = DriverManager.getConnection(url, userName, password);
        } catch (SQLException | ClassNotFoundException e) {
    
            e.printStackTrace();

        }
        return con;
    }

    //  Database query , Return result set 
    public static ResultSet query(Connection con, PreparedStatement st, ResultSet rs, String sql
            , Object[] params) throws SQLException {
    
        st = con.prepareStatement(sql, ResultSet.TYPE_SCROLL_SENSITIVE,
                ResultSet.CONCUR_READ_ONLY);
        if (params != null) {
    
            for (int i = 0; i < params.length; i++) {
    
                st.setObject(i + 1, params[i]);
            }
        }
        rs = st.executeQuery();
        return rs;
    }

    //  Database addition, deletion and modification 
    public static int update(Connection con, String sql
            , Object[] params, ResultSet rs, PreparedStatement st) throws SQLException {
    
        st = con.prepareStatement(sql);
        for (int i = 0; i < params.length; i++) {
    
            st.setObject(i + 1, params[i]);
        }
        return st.executeUpdate();
    }

    //  Close database connection 
    public static void release(Connection con, Statement st, ResultSet rs) {
    
        boolean flag = true;

        if (rs != null) {
    
            try {
    
                rs.close();
                rs = null;
            } catch (SQLException e) {
    
                e.printStackTrace();
                flag = false;
            }
        }

        if (st != null) {
    
            try {
    
                st.close();
                st = null;
            } catch (SQLException e) {
    
                e.printStackTrace();
                flag = false;
            }
        }

        if (con != null) {
    
            try {
    
                con.close();
                con = null;
            } catch (SQLException e) {
    
                e.printStackTrace();
                flag = false;
            }
        }
    }
}

That's what it is Web In the project , Our configuration operations for databases and database operation classes .

establish entity file

Creating entity The function of is to turn each table of the database into an entity in the project entity, This is more in line with Java Object oriented design thinking .

stay entity in , We need to change the data table just created in the database into an entity , For example, in the database user The corresponding is entity Under the user class , The fields in the database correspond to Java Properties in .

User The categories are as follows ：

public class User {
    

    private int uid;
    private String uname;
    private String upassword;
    private Date ucreatetime;

    public int getUid() {
    
        return uid;
    }

    public void setUid(int uid) {
    
        this.uid = uid;
    }

    public String getUname() {
    
        return uname;
    }

    public void setUname(String uname) {
    
        this.uname = uname;
    }

    public String getUpassword() {
    
        return upassword;
    }

    public void setUpassword(String upassword) {
    
        this.upassword = upassword;
    }

    public Date getUcreatetime() {
    
        return ucreatetime;
    }

    public void setUcreatetime(Date ucreatetime) {
    
        this.ucreatetime = ucreatetime;
    }
}

The rest of the database tables correspond to this Java class , And so on .

establish dao Folder

stay dao Under the folder Java It is a file that operates on the underlying database , Is similar to the JDBC To add, delete, modify and check the database , We won't do it today to write the database operation class .

establish filter file

filter The folder is the file where the filter is stored , stay Java Web In the project , We need to let users have access rights , Filter visitor users （ For example, tourists can only view the homepage of the website , Unable to access other pages ）, At this time, you need to use filters to filter permissions . Another application scenario is to use filters to filter character encoding .

establish servlet file

servlet Mainly to respond to the operation of the front end , For example, when the front end needs to log in , Just want to give this request to servlet, And then through this servlet, To encapsulate the data from the front end , Such as user login , Package the front-end data into User class , And then call service Services operate .

establish service file

service The classes in the file are servlet A class is called , adopt servlet The encapsulated class passed , Carry out specific business operations , And call dao Database operation class in layer , Each business can operate the specific data in the database .

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The above is the first step of the project

servlet, And then through this servlet, To encapsulate the data from the front end , Such as user login , Package the front-end data into User class , And then call service Services operate .

establish service file

service The classes in the file are servlet A class is called , adopt servlet The encapsulated class passed , Carry out specific business operations , And call dao Database operation class in layer , Each business can operate the specific data in the database .

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The above is the first step of the project