servlet的用法
1.新建一个类，实现Servlet接口，叫MyServlet
2.实现Servelet的五个方法，在service中做操作
3.配置servlet，<servlet>内部有<servlet-name>、<servlet-class>Servlet-name就是我们给servlet起一个名字Servlet-class写出MyServlet的全限定名
5、配置servlet-mapping，<servlet-mapping>内部有<servlet-name>、<url-pattern>Servlet-name要和之前的servlet中的servlet-name一样url-pattern要和你想访问的url末端一致。
Servlet涉及的设计模式——————适配器设计模式
适配器？
比如说：电脑的电源适配。原本民用电220V，电脑用36V，可见电源的电压需要转化，转化的过程可能很复杂，电源适配器把这一个转化的复杂过程封装到一个小盒子里面
适配器：将一些复杂的功能集成起来，使你不再关注功能的复杂实现，复杂的细节被封装起来了
Servlet-->GenericServlet
Servlet涉及的设计模式------------------模板方法模式
为了专注不同情况做不同的判断，我们设计了模板设计模式，比如说HTTP请求分为很多方式：get、post、put、delete等等
每一种方法我们处理的代码不同
Servet-->GenericServlet---->HttpServlet
Servlet被访问的时候的顺序--------------时序图
自己尝试联系画一个时序图
3.
public class MyServlet extends GenericServlet{
//这个类我们在使用的时候，只需要关注service方法
//其他的问题都被适配器封装了
//现在如果我想使用ServletConfig，this就是ServletConfig
@Override
public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
// TODO Auto-generated method stub
res.getWriter().write("This is GenericServlet");
}
}4.
/**
* Servlet implementation class MyServletConfig
*/
//@WebServlet("/MyServletConfig")
public class MyServletConfig extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public MyServletConfig() {
super();
// TODO Auto-generated constructor stub
}
// private ServletConfig config;
// @Override
// public void init(ServletConfig config) throws ServletException {
// // TODO Auto-generated method stub
// this.config=config;
// }
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.setContentType("text/html;charset=utf-8");
// String username=config.getInitParameter("username");
// String password=config.getI：nitParameter("password");
// String encoding=config.getInitParameter("encoding");
// 获取参数第一种
// String username=getServletConfig().getInitParameter("username");
// String password=getServletConfig().getInitParameter("password");
// String encoding=getServletConfig().getInitParameter("encoding");
//第二种
String username=getInitParameter("username");
String password=getInitParameter("password");
String encoding=getInitParameter("encoding");
response.getWriter().println("第三种方式："+username+":"+password+":"+encoding);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
@WebServlet(
description = "this is myServlet1",
urlPatterns = { "/MyServlet1" },
initParams = {
//@WebInitParam(name = "username", value = "wangwu"),
//@WebInitParam(name = "password", value = "666666")
})
public class MyServlet1 extends HttpServlet {
private static final long serialVersionUID = 1L;
public MyServlet1() {
}
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String username = req.getParameter("username");
String password = req.getParameter("password");
CheckLogin.doLogin(username, password);
System.out.println(username);
resp.getWriter().println(username);
//getServletConfig().getInitParameter(username)
}
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
String username= req.getParameter("username");
String password= req.getParameter("password");
String city= req.getParameter("city");
String sex= req.getParameter("sex");
String hobby[]= req.getParameterValues("hobby");
System.out.println(username+password);
//上述做法并不好，因为属性可能会改变，或者属性多一个就要改很累
User user = new User();
Map<String,String[]> map =req.getParameterMap();
for (Map.Entry<String,String[]> m :map.entrySet()) {
String name= m.getKey();
String values[] = m.getValue();
//使用反射User.class
//属性描述器PropertyDescriptor
//比如说获取User.class中的username成员
//属性描述器描述其username的getUsername()和setUsername()
try {
PropertyDescriptor des =new PropertyDescriptor(name, User.class);
//获取User类的对于name{username,password。。}的set方法
Method me = des.getWriteMethod();
//执行get方法
// if(values.length==1){
// //万一爱好只有一个，也是有问题
// //获取me方法的所有参数类型
//
// Class<?> cls [] = me.getParameterTypes();
// boolean bool = cls[0].isArray();
// if(bool){
// me.invoke(user,(Object) new String[] {values[0]});
// }else{
// me.invoke(user, values[0]);
// }
//
// }else{
// //难点、重点
// //为什么要强转成Object
// //对于me方法，参数可能是多个，于是第二个参数是一个数组
// //当setHobby定义时，唯一的参数是数组，而不是很多个参数组成一个Object[]
// //假设setHobby(String hobby1,String hobby2,String hobby3);
// me.invoke(user, (Object)values);
// }
//最后版本
Class<?> [] cls = me.getParameterTypes();
boolean bool = cls[0].isArray();
if(bool){
me.invoke(user,(Object) new String[] {values[0]});
}else{
me.invoke(user, values[0]);
}
} catch (Exception e) {
e.printStackTrace();
}
}
//System.out.println(user);
}
}
@WebServlet({ "/MyServlet2", "/demo2" })
public class MyServlet2 extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public MyServlet2() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
User user = new User();
Map<String ,String[]> map = req.getParameterMap();
//使用beanutils工具类的populate
try {
BeanUtils.populate(user, map);
} catch (Exception e) {
e.printStackTrace();
}
System.out.println(user);
}
}
@WebServlet({ "/RequestDemo3", "/demo3" })
public class RequestDemo3 extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public RequestDemo3() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
//使用inputStream()
ServletInputStream in=request.getInputStream();
int len=0;
byte [] arr=new byte[1024];
for (;(len=in.read(arr))!=-1;) {
System.out.println(new String(arr,0,arr.length,"utf-8"));
//urlencoder格式数据如下：
//username=%E5%BC%A0%E9%A3%9E%E7%89%9B%E8%82%89&password=123456&sex=%E5%A5%B3&hobby=%E7%AF%AE%E7%90%83&hobby=%E7%BE%BD%E6%AF%9B%E7%90%83&city=%E5%B9%BF%E5%B7%9E
//urldecoder可以把数据还原：
//
System.out.println(URLDecoder.decode(new String(arr,0,arr.length,"utf-8"),"utf-8"));
}
in.close();
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
@WebServlet("/demo4")
public class RequestDemo4 extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public RequestDemo4() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
//request.setCharacterEncoding(env);
//Tomcat7.x中默认使用的字符编码是ISO-8859-1
String username=request.getParameter("username");
//此时是乱码，它是iso-8859-1
System.out.println(username);
//把乱码的数据还原成01010101的二进制状态
byte [] arr=username.getBytes("ISO-8859-1");
//把二进制状态的数据变为utf-8格式的数据
username=new String(arr,"utf-8");
//此时username就不乱码了
System.out.println(username);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
@WebServlet("/demo5")
public class RequestDemo5 extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public RequestDemo5() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
//请求转发：
//发现转走了request，那么request中的参数也就随着转发过去了
request.getRequestDispatcher("/demo1").forward(request, response);
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}