JDBC+Servlet+JSP的学生案例增删改查

数据库信息传输到页面实现。

先进行学生信息页面展示：

接口IStudentDao

public interface IStudentDao {
    /**
     * 保存操作
     * @param stu 学生对象，封装了需要保存的对象
     */
    void save(Student stu);

    /**
     * 删除操作
     * @param id 被删除学生的主键操作
     */
    void delete(Long id);
    /**
     *
     * @param id    被更改学生的主键值
     * @param newStu    学生新的信息
     */
    void update(Student newStu);
    /**
     * 查询指定id的学生对象
     * @param id    被查询学生的主键值
     * @return         如果id存在，返回学生对象，否则为null
     */
    Student get(Long id);
    /**
     * 查询并返回所有学生对象
     * @return 如果结果集为空，返回一个空的list对象
     */
    List<Student> listall();
}

IStudentDaoImpl

public class IStudentDaoImpl implements IStudentDao{

    public void save(Student stu) {
        String sql ="insert into t_student (name,age) values (?,?)";
        PreparedStatement ps = null;
        //贾琏
        Connection conn = null;
        try {
            conn = JDBCUtil.getConn();
            ps = conn.prepareStatement(sql);//欲
            ps.setString(1, stu.getName());
            ps.setInt(2, stu.getAge());
            ps.executeUpdate();//执行
        } catch (SQLException e) {
            e.printStackTrace();
        }
        JDBCUtil.close(conn, ps, null);//事务

    }

    @Override
    public void delete(Long id) {
        String sql ="delete from t_student where id = ?";
        PreparedStatement ps =null;
        //贾琏
        Connection conn = null;
        try {
            conn = JDBCUtil.getConn();
            ps =conn.prepareStatement(sql);
            ps.setLong(1, id);
            ps.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        }
        JDBCUtil.close(conn, ps, null);
    }
    //update t_student set name='xx',age=17 where id=12
    @Override
    public void update(Student stu) {
        String sql="update t_student set name =? ,age=? where id=?";
        PreparedStatement ps =null;
        //贾琏
        Connection conn =null;
        try {

            conn = JDBCUtil.getConn();
            ps=conn.prepareStatement(sql);
            ps.setString(1, stu.getName());
            ps.setInt(2, stu.getAge());
            ps.setLong(3, stu.getId());
            ps.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        }
        JDBCUtil.close(conn, ps, null);
    }

    public Student get(Long id) {
        String sql ="select * from t_student where id=?";
        PreparedStatement ps =null;
        //贾琏
        Connection conn =null;
        ResultSet rs = null;
        try {
            conn = JDBCUtil.getConn();
            ps = conn.prepareStatement(sql);
            ps.setLong(1, id);
            rs= ps.executeQuery();
            if (rs.next()) {
                Student stu = new Student();
                stu.setId(rs.getLong("id"));
                stu.setName(rs.getString("name"));
                stu.setAge(rs.getInt("age"));
                return stu;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        JDBCUtil.close(conn, ps, rs);
        return null;
    }

    @Override
    public List<Student> listall() {
        List<Student> list = new ArrayList<>();
        String sql ="select * from t_student";
        PreparedStatement ps = null;
        Connection conn = null;
        ResultSet rs =null;
        try {
            conn = JDBCUtil.getConn();
            ps = conn.prepareStatement(sql);
            rs = ps.executeQuery();
            while(rs.next()){
                Student stu = new Student();
                stu.setId(rs.getLong("id"));
                stu.setName(rs.getString("name"));
                stu.setAge(rs.getInt("age"));
                list.add(stu);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            JDBCUtil.close(conn, ps, rs);
        }
        return list;

    }

domain类

public class Student {
    private Long id;
    private String name;
    private Integer age;
    public Student(){}
    public Student(String name,Integer age){
        this.age=age;
        this.name=name;
    }
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + ", age=" + age + "]";
    }

}

设计个util类，方便维护

public class JDBCUtil {
    private static DataSource ds =null;
    static{
        //当JDBCUtil执行后，直接加载至JVM就立即执行
        try {
            Properties p = new Properties();
            p.load(Thread.currentThread().getContextClassLoader().getResourceAsStream("db.properties"));
            ds = DruidDataSourceFactory.createDataSource(p);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public static Connection getConn(){
        try {
            return ds.getConnection();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }
    public static void close(Connection conn,Statement st,ResultSet rs){
        try {
            if (rs!=null) {
                rs.close();
            }
        } catch (Exception e) {
        }finally {
            try {
                if (st!=null) {
                    st.close();
                }
            } catch (Exception e) {
                e.printStackTrace();
            }finally {
                try {
                    if (conn!=null) {
                        conn.close();
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

在网页展示全部信息，将数据用student传输过去，在前台获取。

@WebServlet("/student/list")
public class ListStudentServlet extends HttpServlet{
    private static final long serialVersionUID = 1L;
    private IStudentDao dao;
    @Override
    public void init() throws ServletException {
        dao = new IStudentDaoImpl();
    }
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.接收请求参数封装成对象

        //2.调用业务方法处理请求
        List<Student> list = dao.listall();
        req.setAttribute("students", list);

        //3.控制界面跳转
        req.getRequestDispatcher("/WEB-INF/view/student/list.jsp").forward(req, resp);

    }
}

${student}获取后端传输过来的数据。然后c:forEach展示。

<h2 align="center"> 学生列表</h2>
    <a href="/student/edit">添加学生</a>
     <table border="1" width="50%" cellpadding="0" cellspacing="0" align="center">
         <tr style="background-color: orange;">
             <th>编号</th>
             <th>姓名</th>
             <th>年龄</th>
             <th>操作</th>
         </tr>

     <c:forEach items="${students}" var="s" varStatus="vs">
         <tr style='background-color: ${vs.count %2==0 ?"LavenderBlush":"gray"};'>
             <td>${s.id }</td>
             <td>${s.name }</td>
             <td>${s.age }</td>
             <td>
                 <a href="/student/delete?id=${s.id}">删除</a>     |
                 <a href="/student/edit?id=${s.id}">编辑</a>
             </td>
         </tr>
    </c:forEach>
     </table>

删除操作传输一个id值，/student/delete?id=${s.id}删除指定的一条数据。然后返回到原来的界面

@WebServlet("/student/delete")
public class DeleteStudentServlet extends HttpServlet{
    private static final long serialVersionUID= 1L;
    private IStudentDao dao;
    @Override
    public void init() throws ServletException {
        dao=new IStudentDaoImpl();
    }
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.接收请求参数封装成对象
        Long id = Long.valueOf(req.getParameter("id"));
        //2.调用业务方法处理请求
        dao.delete(id);
        //3.控制界面跳转
        resp.sendRedirect("/student/list");
    }

}

增加和删除操作的区别在于传输的数据是否有id值，需要进行判断，当传输的数据没有id的时候，就进行增加操作

@WebServlet("/student/edit")
public class EditStudentServlet extends HttpServlet{
    private static final long serialVersionUID=1L;
    private IStudentDao dao;
    @Override
    public void init() throws ServletException {
        dao=new IStudentDaoImpl();
    }

    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.接收请求参数封装成对象
        String sid = req.getParameter("id");

        //2.调用业务方法处理请求
        if (hasLength(sid)) {
            Student stu = dao.get(Long.valueOf(sid));
            req.setAttribute("student", stu);//传递给edit.jsp,用于回显被编辑的学生。
        }
        //3.控制界面跳转
        req.getRequestDispatcher("/WEB-INF/view/student/edit.jsp").forward(req, resp);
    }
    private boolean hasLength(String str){
        return str!=null &&!"".equals(str.trim());
    }
}

edit.jsp

    <form action="/student/save" method="post">
        <input type="hidden" name="id" value="${student.id }">
        姓名<input type="text" name="name" required value="${student.name }"/><br/>
        年纪<input type="number" name="age" required value="${student.age }"><br/>

        <input type="submit" value="${student==null ?"保存学生信息":"修改学生信息"}">
    </form>

根据id值有无判断进行什么操作

@WebServlet("/student/save")
//保存学生信息
public class SaveStudentServlet extends HttpServlet{
    private static final long serialVersionUID =1L;
    private IStudentDao dao;
    @Override
    public void init() throws ServletException {
        dao = new IStudentDaoImpl();
    }

    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.接收请求参数封装成对象
        req.setCharacterEncoding("UTF-8");
        String name = req.getParameter("name");
        Integer age = Integer.valueOf(req.getParameter("age"));
        Student stu = new Student(name, Integer.valueOf(age));
        //2.调用业务方法处理请求
        String id = req.getParameter("id");
        if (hasLength(id)) {//更新保存
            stu.setId(Long.valueOf(id));
            dao.update(stu);
        }else {            //新增
            dao.save(stu);
        }
        //3.控制界面跳转
        resp.sendRedirect("/student/list");

    }
    private boolean hasLength(String str){
        return str!=null &&!"".equals(str.trim());
    }
}

以上就可以进行简单的增删改查操作