Druid

下面我们讲的是在javaweb中对于Durid的使用，我们通过JDBC来连接数据库，我们会在一个登录案例中了解，在web项目中如何获取数据库连接对象。

这是JDBCUtils类相当于JDBC的工具类

public class JDBCUtils {
    private static DataSource ds;
    static {
        try {
        //1.加载配置文件，获取字节输入流
        Properties props = new Properties();
        //使用ClassLoder加载配置文件获取字节输入流
//        InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");
//        props.load(is);
        props.load(new FileReader("C:\Users\86157\Desktop\javatest\JavaWeb\Servlet\src\druid.properties"));
        //初始化连接池对象
        ds = DruidDataSourceFactory.createDataSource(props);

        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    //获取连接池对象
    public static DataSource getDataSource(){
        return ds;
    }
    //获取Connection对象
    public static Connection getConnection() throws SQLException {
        return ds.getConnection();
    }
}

这个呢是我们的连接JDBC的druid.properties配置文件

#driverClassName=com.mysql.jdbc.Driver
driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql:///javaee
username=root
password=123456
initialSize=5
maxActive=200
maxWait=5000

接下来我们创建一个用户实体类，此类用来对接数据库中的数据

public class User {
    private int id;
    private String username;
    private String password;

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + ''' +
                ", password='" + password + ''' +
                '}';
    }

    public int getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

UserDao这个类呢，是用来匹配用户名和密码的。

利用template中的queryForObject方法执行sql，并把查询的到的user对象返回

public class UserDao {
    //声明JDBCTemplate对象共用
    private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());
    
    public User login(User loginUser) {
        try {
            //1.编写sql
            String sql = "select * from user where username = ? and password = ?";
            //2.调用query方法
            User user = template.queryForObject(sql,
                    new BeanPropertyRowMapper(User.class),
                    loginUser.getUsername(), loginUser.getPassword());
            return user;
        } catch (DataAccessException e) {
            e.printStackTrace();//记录日志
            return null;
        }
    }
}

下面是整个代码最核心的部分

登录页面的核心代码

@WebServlet("/LoginServlet")
public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.设置编码
        req.setCharacterEncoding("utf-8");
       
        //2.获取所有请求参数
        Map map = req.getParameterMap();
        //3.创建User对象
        User loginUser = new User();
        //3.2使用BeanUtils封装
        try {
            BeanUtils.populate(loginUser,map);
        } catch (IllegalAccessException | InvocationTargetException e) {
            e.printStackTrace();
        }


        //4.调用UserDao的login方法
        UserDao dao = new UserDao();
        User user = dao.login(loginUser);

        //5.判断user
        if(user == null){
            //登录失败
            req.getRequestDispatcher("/failServlet").forward(req,resp);
        }else{
            //登录成功
            //存储数据
            req.setAttribute("user",user);
            //转发
            req.getRequestDispatcher("/successServlet").forward(req,resp);
        }

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

一开始我们用的是这个方法获取的用户名和密码

	    //2.获取请求参数
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        //3.封装user对象
        User loginUser = new User();
        loginUser.setUsername(username);
        loginUser.setPassword(password);

后来我们用

request中的getParameterMap方法获取全部参数然后封装对象

    //2.获取所有请求参数
    Map map = req.getParameterMap();
    //3.创建User对象
    User loginUser = new User();
    //3.2使用BeanUtils封装
    try {
        BeanUtils.populate(loginUser,map);
    } catch (IllegalAccessException | InvocationTargetException e) {
        e.printStackTrace();
    }

然后是我们登录成功的页面和失败的页面

@WebServlet("/failServlet")
public class FailServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //给页面写一句话

        //设置编码
        response.setContentType("text/html;charset=utf-8");
        //输出
        response.getWriter().write("登录失败，用户名或密码错误");

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }
}

@WebServlet("/successServlet")
public class SuccessServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取request域中共享的user对象
        User user = (User) request.getAttribute("user");

        if(user != null){
            //给页面写一句话

            //设置编码
            response.setContentType("text/html;charset=utf-8");
            //输出
            response.getWriter().write("登录成功！"+user.getUsername()+",欢迎您");
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }
}