使用servlet将图片保存到数据库中

news2024/11/19 1:34:38

一、导入jar包，配置properties文件（src路径下）

commons-fileupload-1.3.1.jar
commons-io-2.2.jar
druid-1.2.8.jar
mysql-connector-java-8.0.25.jar
servlet-api.jar

#   ????key-value???
driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/数据库名
username=数据库用户名
password=数据库用户密码
# init size
initialSize=5
# max size
maxActive=10
maxWait=3000

二、用html写一个简易的网页

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h3>添加老师信息</h3>
<form action="teacherServlet" method="post" enctype="multipart/form-data">
    <input type="hidden" name="action" value="add">
    姓名：<input type="text" name="name"><br/>
    年龄：<input type="text" name="age"><br/>
    出生日期：<input type="date" name="birthday"><br/>
    头像：<input type="file" name="tx" ><br/>
    <input type="submit" value="添加">
</form>

</body>
</html>

三、根据表单数据建立好对应的数据库JDBC连接

详情见链接：https://blog.csdn.net/qq_62182919/article/details/142220224?sharetype=blogdetail&sharerId=142220224&sharerefer=PC&sharesource=qq_62182919&sharefrom=from_link

四、创建TeacherServlet ，完成请求响应

因为在上方表单要将图片以二进制字节流上传，所以用到了enctype=“multipart/form-data”
相对应的在Servlet中
@MultipartConfig // 一定要加注解

//  1.设置编码方式
@WebServlet("/teacherServlet")
@MultipartConfig            //  一定要加注解
public class TeacherServlet extends HttpServlet {
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("utf-8");
        resp.setCharacterEncoding("utf-8");
        resp.setContentType("text/html;charset=utf-8");
        System.out.println("添加学生信息！");
            //  处理请求信息
            String name = req.getParameter("name");
            Integer age = Integer.parseInt(req.getParameter("age"));
            String date = req.getParameter("birthday");
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
            Date birthday = null;
            try {
                birthday = sdf.parse(date);
            } catch (ParseException e) {
                throw new RuntimeException(e);
            }
            //  获取头像的文件信息并进行处理
            Part part = req.getPart("tx");
            String filename = part.getSubmittedFileName();
            filename = UUID.randomUUID().toString().replace("-","")+"-"+filename;
            //  将图片上传到指定路径
            String path = "E:\\学习日记\\07javaEE课堂笔记\\img\\"+filename;
            //  上传
            part.write(path);
            //  把文件名作为数据保存到数据库之中
            Teacher teacher = new Teacher(name,age,birthday,filename);
            int num = new TeacherDao().addTeacher(teacher);
            if(num!=0){
                System.out.println("添加成功！");
                resp.sendRedirect("teacherServlet?action=selectAll");
            }else{
                resp.getWriter().write("<h1>添加失败！</h1>");
            }
    }
    }

五、根据数据库中保存的文件名预览保存在对应文件夹的图片servlet实现请求

//  预览图片
@WebServlet("/down")
public class DownloadServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //  1.设置编码方式
        req.setCharacterEncoding("utf-8");
        resp.setCharacterEncoding("utf-8");
        resp.setContentType("text/html;charset=utf-8");
        //  2.处理请求信息
        String filename = req.getParameter("filename");
        //  3.以字节流的形式把图片响应给前端
        FileInputStream fin = new FileInputStream(new File("E:\\学习日记\\07javaEE课堂笔记\\img",filename));
        //  设置响应的图片是1预览还是下载到本地
        //  预览：resp.setHeader("Content-Disposition", "filename="+filename);
        //  下载：resp.setHeader("Content-Disposition", "attachment;filename="+filename);
        resp.setHeader("Content-Disposition", "filename="+filename);
        ServletOutputStream out = resp.getOutputStream();
        //  读写操作
        byte b[] = new byte[1024];
        int len = 0;
        while((len=fin.read(b))!=-1){
            out.write(b,0,len);
        }
        out.close();
        fin.close();
    }
}

六、简易的页面用来展示数据库中的数据

在另一个servlet中可以通过下面的响应请求的方式，将需要的网页直接编写出来（注意设置代码编写格式）
预览图片用到了请求 down
out.write(“”);

            PrintWriter out = resp.getWriter();
            out.write("<table border=1>");
            //  表头
            out.write("<tr><th>编号</th><th>姓名</th><th>年龄</th><th>出生日期</th><th>操作</th></tr>");
            //  表格内容
            //  连接数据库，查询所有的老师信息
            List<Teacher> teachers = new TeacherDao().findTeachers();
            for(Teacher teacher:teachers){
                out.write("<tr>");
                out.write("<td>"+teacher.getId()+"</td>");
                out.write("<td>"+teacher.getName()+"</td>");
                out.write("<td>"+teacher.getAge()+"</td>");
                out.write("<td>"+teacher.getBirthday()+"</td>");
                out.write("<td><img src='down?filename="+teacher.getTx()+"' width='200'></td>");
                out.write("<td><a href='teacherServlet?action=del&id="+teacher.getId()+"'>删除</a>"
//                        + "<a href='teacherServlet?action=update&id="+teacher.getId()+"&name="+teacher.getName()+"&age="+teacher.getAge()+"&birthday="+teacher.getBirthday()+"'>修改</a>"
                        + "</td>");
                out.write("</tr>");
            }
            out.write("</table>");
            out.write("<a href='add.html'>添加老师信息</a>");