Servlet运行过程
Servlet实现类
使用IDEA开发Servlet
Servlet映射路径问题
1.一般情况下我们都会指定一个URL , 一个URL对应一个请求
2.通配问题
- /* :不报错
- *.do
重定向
将这个请求,转换到另一个地址;
比如,我们请求 : http://localhost:8080/servlet01/dasdasdasda/aaaa.do 他会跳转到百度首页;
//通过响应对象重定向页面
resp.sendRedirect("404.jsp");
ServletContext
通过servletContext对象读取网站配置文件
- 新建一个properties文件
driver=com.mysql.jdbc.Driver
username=root
password=123456
url=jdbc:mysql://localhost:3306/smbms
- 编写servlet类
//读取properties配置文件
public class ServletDemo03 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//读取配置文件
//1.获得配置文件的路径
String realPath = this.getServletContext().getRealPath("/WEB-INF/classes/resources/database.properties");
System.out.println("取得的路径为:"+realPath);
Properties properties = new Properties();
FileInputStream is = new FileInputStream(realPath);
properties.load(is);//把文件流加载到配置文件的对象中;
String driver = properties.getProperty("driver");
String username = properties.getProperty("username");
String password = properties.getProperty("password");
String url = properties.getProperty("url");
//响应到网页
resp.getWriter().println(driver);
resp.getWriter().println(username);
resp.getWriter().println(password);
resp.getWriter().println(url);
//=======================================
System.out.println(driver);
System.out.println(username);
System.out.println(password);
System.out.println(url);
}
}
- 配置web.xml
<servlet>
<servlet-name>Demo03</servlet-name>
<servlet-class>com.kuang.servlet.ServletDemo03</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Demo03</servlet-name>
<url-pattern>/q3</url-pattern>
</servlet-mapping>
- 访问查看
localhost:8080/demo02/q3
简单验证码
//验证码
public class ServletDemo04 extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doPost(req,resp);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//resp.getWriter().println(newRandom());
//自动刷新网页
resp.setHeader("refresh","2");
//验证码是一个图片 , 我们需要制作一个图片
BufferedImage image = new BufferedImage(100,30,BufferedImage.TYPE_3BYTE_BGR);
//图片写入一些东西
Graphics2D graphics = image.createGraphics();
graphics.setColor(Color.red);
String num = String.valueOf(newRandom());
graphics.drawString(num,10,10);
//想办法让浏览器知道我们给的是一张图片
resp.setContentType("image/jpg");
//让网站去打开图片
ImageIO.write(image,"jpg",resp.getOutputStream());
}
//生成随机数
public int newRandom(){
int num = (int)(Math.random()*9+1)*100000;
return num;
}
/*
@Test
public void test(){
ServletDemo04 servletDemo04 = new ServletDemo04();
for (int j = 0; j < 100; j++) {
int i = servletDemo04.newRandom();
System.out.println(i);
}
}
*/
}