使用Java实现数据库编程 1．创建数据库表apply_info，添加测试数据不少于4条， 2．创建实体类ApplyInfo，根据业务提供需要的构造方法和setter/getter方法 3．创建BaseDao类，实现数据库连接和关闭功能 4．创建DAO接口ApplyInfoDao，定义学生报名，按班级查询，按比赛项目，取消报名的方法 5．创建DAO实现类ApplyInfoDaoImpl，实现ApplyInfoDao接口，使用JDBC完成相应数据库操作 6．创建Service接口ApplyInfoService，定义学生报名，按班级查询，按比赛项目，取消报名的方法 7．创建Service实现类ApplyInfoServiceImpl，实现ApplyInfoService接口，调用Dao层方法实现数据操作 8．创建ApplyMgr类，完成在控制台的报名信息操作，启动和运行系统 9．全部功能测试正常

下面是使用Java实现数据库编程的详细步骤：

1. 创建数据库表apply_info，添加测试数据不少于4条

首先，需要在数据库中创建一个名为apply_info的表，并添加至少4条测试数据。可以使用以下SQL语句：

CREATE TABLE apply_info (
    id INT NOT NULL AUTO_INCREMENT,
    name VARCHAR(50) NOT NULL,
    gender VARCHAR(10) NOT NULL,
    class VARCHAR(50) NOT NULL,
    project VARCHAR(50) NOT NULL,
    PRIMARY KEY (id)
);

INSERT INTO apply_info (name, gender, class, project) VALUES ('Tom', 'Male', 'Class 1', 'Running');
INSERT INTO apply_info (name, gender, class, project) VALUES ('Lucy', 'Female', 'Class 2', 'Swimming');
INSERT INTO apply_info (name, gender, class, project) VALUES ('John', 'Male', 'Class 3', 'Long jump');
INSERT INTO apply_info (name, gender, class, project) VALUES ('Jane', 'Female', 'Class 4', 'High jump');

2. 创建实体类ApplyInfo，根据业务提供需要的构造方法和setter/getter方法

创建一个名为ApplyInfo的Java类，该类对应数据库中的apply_info表。该类应该包含以下属性：

private int id;
private String name;
private String gender;
private String class;
private String project;

同时，应该提供构造方法和setter/getter方法。

public class ApplyInfo {
    private int id;
    private String name;
    private String gender;
    private String class;
    private String project;

    public ApplyInfo() {}

    public ApplyInfo(String name, String gender, String class, String project) {
        this.name = name;
        this.gender = gender;
        this.class = class;
        this.project = project;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public String getClass() {
        return class;
    }

    public void setClass(String class) {
        this.class = class;
    }

    public String getProject() {
        return project;
    }

    public void setProject(String project) {
        this.project = project;
    }
}

3. 创建BaseDao类，实现数据库连接和关闭功能

创建一个名为BaseDao的Java类，该类应该包含连接数据库和关闭数据库连接的方法。

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class BaseDao {
    private static final String URL = "jdbc:mysql://localhost:3306/test?useSSL=false&serverTimezone=UTC";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "root";

    public Connection getConnection() throws SQLException {
        return DriverManager.getConnection(URL, USERNAME, PASSWORD);
    }

    public void closeConnection(Connection conn) throws SQLException {
        if (conn != null) {
            conn.close();
        }
    }
}

4. 创建DAO接口ApplyInfoDao，定义学生报名，按班级查询，按比赛项目，取消报名的方法

创建一个名为ApplyInfoDao的Java接口，该接口定义了对数据库中apply_info表的各种操作方法，包括学生报名、按班级查询、按比赛项目查询和取消报名。

import java.sql.SQLException;
import java.util.List;

public interface ApplyInfoDao {
    void add(ApplyInfo info) throws SQLException;
    void delete(int id) throws SQLException;
    List<ApplyInfo> getByClass(String className) throws SQLException;
    List<ApplyInfo> getByProject(String projectName) throws SQLException;
}

5. 创建DAO实现类ApplyInfoDaoImpl，实现ApplyInfoDao接口，使用JDBC完成相应数据库操作

创建一个名为ApplyInfoDaoImpl的Java类，该类实现了ApplyInfoDao接口，并使用JDBC完成相应的数据库操作。

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class ApplyInfoDaoImpl extends BaseDao implements ApplyInfoDao {
    private static final String ADD_SQL = "INSERT INTO apply_info (name, gender, class, project) VALUES (?, ?, ?, ?)";
    private static final String DELETE_SQL = "DELETE FROM apply_info WHERE id=?";
    private static final String GET_BY_CLASS_SQL = "SELECT * FROM apply_info WHERE class=?";
    private static final String GET_BY_PROJECT_SQL = "SELECT * FROM apply_info WHERE project=?";

    @Override
    public void add(ApplyInfo info) throws SQLException {
        Connection conn = null;
        PreparedStatement stmt = null;
        try {
            conn = getConnection();
            stmt = conn.prepareStatement(ADD_SQL);
            stmt.setString(1, info.getName());
            stmt.setString(2, info.getGender());
            stmt.setString(3, info.getClass());
            stmt.setString(4, info.getProject());
            stmt.executeUpdate();
        } finally {
            if (stmt != null) {
                stmt.close();
            }
            closeConnection(conn);
        }
    }

    @Override
    public void delete(int id) throws SQLException {
        Connection conn = null;
        PreparedStatement stmt = null;
        try {
            conn = getConnection();
            stmt = conn.prepareStatement(DELETE_SQL);
            stmt.setInt(1, id);
            stmt.executeUpdate();
        } finally {
            if (stmt != null) {
                stmt.close();
            }
            closeConnection(conn);
        }
    }

    @Override
    public List<ApplyInfo> getByClass(String className) throws SQLException {
        Connection conn = null;
        PreparedStatement stmt = null;
        ResultSet rs = null;
        List<ApplyInfo> result = new ArrayList<>();
        try {
            conn = getConnection();
            stmt = conn.prepareStatement(GET_BY_CLASS_SQL);
            stmt.setString(1, className);
            rs = stmt.executeQuery();
            while (rs.next()) {
                ApplyInfo info = new ApplyInfo();
                info.setId(rs.getInt("id"));
                info.setName(rs.getString("name"));
                info.setGender(rs.getString("gender"));
                info.setClass(rs.getString("class"));
                info.setProject(rs.getString("project"));
                result.add(info);
            }
            return result;
        } finally {
            if (rs != null) {
                rs.close();
            }
            if (stmt != null) {
                stmt.close();
            }
            closeConnection(conn);
        }
    }

    @Override
    public List<ApplyInfo> getByProject(String projectName) throws SQLException {
        Connection conn = null;
        PreparedStatement stmt = null;
        ResultSet rs = null;
        List<ApplyInfo> result = new ArrayList<>();
        try {
            conn = getConnection();
            stmt = conn.prepareStatement(GET_BY_PROJECT_SQL);
            stmt.setString(1, projectName);
            rs = stmt.executeQuery();
            while (rs.next()) {
                ApplyInfo info = new ApplyInfo();
                info.setId(rs.getInt("id"));
                info.setName(rs.getString("name"));
                info.setGender(rs.getString("gender"));
                info.setClass(rs.getString("class"));
                info.setProject(rs.getString("project"));
                result.add(info);
            }
            return result;
        } finally {
            if (rs != null) {
                rs.close();
            }
            if (stmt != null) {
                stmt.close();
            }
            closeConnection(conn);
        }
    }
}

6. 创建Service接口ApplyInfoService，定义学生报名，按班级查询，按比赛项目，取消报名的方法

创建一个名为ApplyInfoService的Java接口，该接口定义了对学生报名信息的各种操作方法，包括学生报名、按班级查询、按比赛项目查询和取消报名。

import java.sql.SQLException;
import java.util.List;

public interface ApplyInfoService {
    void add(ApplyInfo info) throws SQLException;
    void delete(int id) throws SQLException;
    List<ApplyInfo> getByClass(String className) throws SQLException;
    List<ApplyInfo> getByProject(String projectName) throws SQLException;
}

7. 创建Service实现类ApplyInfoServiceImpl，实现ApplyInfoService接口，调用Dao层方法实现数据操作

创建一个名为ApplyInfoServiceImpl的Java类，该类实现了ApplyInfoService接口，并调用Dao层方法实现数据操作。

import java.sql.SQLException;
import java.util.List;

public class ApplyInfoServiceImpl implements ApplyInfoService {
    private ApplyInfoDao dao = new ApplyInfoDaoImpl();

    @Override
    public void add(ApplyInfo info) throws SQLException {
        dao.add(info);
    }

    @Override
    public void delete(int id) throws SQLException {
        dao.delete(id);
    }

    @Override
    public List<ApplyInfo> getByClass(String className) throws SQLException {
        return dao.getByClass(className);
    }

    @Override
    public List<ApplyInfo> getByProject(String projectName) throws SQLException {
        return dao.getByProject(projectName);
    }
}

8. 创建ApplyMgr类，完成在控制台的报名信息操作，启动和运行系统

创建一个名为ApplyMgr的Java类，该类用于在控制台上完成学生报名信息的各种操作。

import java.sql.SQLException;
import java.util.List;
import java.util.Scanner;

public class ApplyMgr {
    private ApplyInfoService service = new ApplyInfoServiceImpl();
    private Scanner scanner = new Scanner(System.in);

    public void start() throws SQLException {
        System.out.println("Welcome to apply information system!");
        while (true) {
            System.out.println("Please choose your operation:");
            System.out.println("1. Add apply information");
            System.out.println("2. Delete apply information");
            System.out.println("3. Get apply information by class");
            System.out.println("4. Get apply information by project");
            System.out.println("5. Exit");

            String choice = scanner.nextLine();
            switch (choice) {
                case "1":
                    addApplyInfo();
                    break;
                case "2":
                    deleteApplyInfo();
                    break;
                case "3":
                    getApplyInfoByClass();
                    break;
                case "4":
                    getApplyInfoByProject();
                    break;
                case "5":
                    System.out.println("Thanks for using apply information system!");
                    return;
                default:
                    System.out.println("Invalid choice, please try again.");
            }
        }
    }

    private void addApplyInfo() throws SQLException {
        System.out.println("Please input name:");
        String name = scanner.nextLine();
        System.out.println("Please input gender:");
        String gender = scanner.nextLine();
        System.out.println("Please input class:");
        String clazz = scanner.nextLine();
        System.out.println("Please input project:");
        String project = scanner.nextLine();

        ApplyInfo info = new ApplyInfo(name, gender, clazz, project);
        service.add(info);
        System.out.println("Add apply information successfully!");
    }

    private void deleteApplyInfo() throws SQLException {
        System.out.println("Please input id:");
        int id = Integer.parseInt(scanner.nextLine());
        service.delete(id);
        System.out.println("Delete apply information successfully!");
    }

    private void getApplyInfoByClass() throws SQLException {
        System.out.println("Please input class:");
        String clazz = scanner.nextLine();
        List<ApplyInfo> result = service.getByClass(clazz);
        if (result.isEmpty()) {
            System.out.println("No apply information found.");
        } else {
            System.out.println("Apply information list:");
            for (ApplyInfo info : result) {
                System.out.println(info.getId() + "\t" + info.getName() + "\t" + info.getGender() + "\t" + info.getClass() + "\t" + info.getProject());
            }
        }
    }

    private void getApplyInfoByProject() throws SQLException {
        System.out.println("Please input project:");
        String project = scanner.nextLine();
        List<ApplyInfo> result = service.getByProject(project);
        if (result.isEmpty()) {
            System.out.println("No apply information found.");
        } else {
            System.out.println("Apply information list:");
            for (ApplyInfo info : result) {
                System.out.println(info.getId() + "\t" + info.getName() + "\t" + info.getGender() + "\t" + info.getClass() + "\t" + info.getProject());
            }
        }
    }

    public static void main(String[] args) throws SQLException {
        ApplyMgr mgr = new ApplyMgr();
        mgr.start();
    }
}

9. 全部功能测试正常

运行ApplyMgr类，测试所有功能是否正常。如果全部功能都能够正常使用，则说明Java数据库编程已经成功实现。