1 Request

1.1 Request继承关系

ServletRequest     Java提供的请求对象根接口
HttpServletRequest Java提供的对Http协议封装的请求对象接口
RequestFacade	   Tomcat定义的实现类

@WebServlet("/demo2")
public class Servlet2Demo extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println("doGet req = " + req);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println("doPost");}
}

请求http://localhost:8080/tomcat-demo/demo2后，输出日志

doGet req = org.apache.catalina.connector.RequestFacade@1184683

所以继承关系为

RequestFacade extends HttpServletRequest extends ServletRequest

1.2 Request请求数据

1.2.1 获取请求行数据

@WebServlet("/demo2")
public class Servlet2Demo extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {String method = req.getMethod();System.out.println("method = " + method);String path = req.getContextPath();System.out.println("path = " + path);StringBuffer url = req.getRequestURL();System.out.println("url = " + url);String uri = req.getRequestURI();System.out.println("uri = " + uri);String queryString = req.getQueryString();System.out.println("queryString = " + queryString);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println("doPost");}
}

请求地址: http://localhost:8080/tomcat-demo/demo2?username=zhangsan&pwd=123
输出结果

method = GET
path = /tomcat-demo
url = http://localhost:8080/tomcat-demo/demo2
uri = /tomcat-demo/demo2
queryString = username=zhangsan&pwd=123

1.2.2 获取请求头数据

代码示例

String agent = req.getHeader("user-agent");
System.out.println("agent = " + agent);

输出结果

agent = Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) 
AppleWebKit/537.36 (KHTML, like Gecko) Chrome/107.0.0.0 Safari/537.36

1.2.3 获取请求体数据

1 在webApp包下创建req.html

2 在Servlet#doPost()方法中获取数据

@WebServlet("/req1")
public class RequestDemo1 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {BufferedReader bufferedReader = req.getReader();String line = bufferedReader.readLine();System.out.println(line);}}

3 启动服务，通过浏览器请求

http://localhost:8080/tomcat-demo/req.html

4 在html页面中输入内容后提交后，可看到日志输出

username=zhang&password=1123

1.2.4 获取请求参数的通用方式

1 doGet()和doPost()方法获取到的参数相同时

@WebServlet("/req1")
public class RequestDemo1 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {String result = req.getQueryString();System.out.println(result);//和doPost()方法的代码相同}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {BufferedReader bufferedReader = req.getReader();String line = bufferedReader.readLine();System.out.println(line);//和doGet()方法中的代码相同}}

2 处理上述问题方式1
直接在doPost()方法中调用doGet()方法

 @WebServlet("/req1")
public class RequestDemo1 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {String params = "";String method = req.getMethod();if ("GET".equals(method)) {params = req.getQueryString();} else if("POST".equals(method)) {BufferedReader reader = req.getReader();params = reader.readLine();}System.out.println(params);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}}

3 方式二
html代码

 跑步 骑车

Servlet代码

@WebServlet("/req2")
public class RequestDemo2 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//获得所有参数Map map = req.getParameterMap();for (String key : map.keySet()) {System.out.println("key ---> "  + key);String [] values = map.get(key);for (String value : values) {System.out.println("value ---> " + value);}System.out.println();}// 获得单个参数String username = req.getParameter("username");String password = req.getParameter("password");System.out.println("单个参数值 username = " + username + ", password = " + password);//数组值String[] hobbies = req.getParameterValues("hobby");for (String hobby: hobbies) {System.out.println(hobby);}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {super.doPost(req, resp);}
}

访问http://localhost:8080/tomcat-demo/req.html 后
日志输出

key ---> username
value ---> lisikey ---> password
value ---> 432key ---> hobby
value ---> 1
value ---> 2单个参数值 username = lisi, password = 432
1
2

1.3 乱码问题

//=================乱码问题//post方式设置解码格式
//        req.setCharacterEncoding("UTF-8");//get/post设置解码格式username = new String(username.getBytes("ISO-8859-1"), "UTF-8");System.out.println("username = " + username);

日志输出

单个参数值 username = å¼ ä¸‰, password = 321
1
2
username = 张三

1.3 请求转发

@WebServlet("/req3")
public class RequestDemo3 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println("req3 doGet ---> ");req.setAttribute("key_req", "value from req3");//转发req.getRequestDispatcher("/req4").forward(req, resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {super.doPost(req, resp);}
}

@WebServlet("/req4")
public class RequestDemo4 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println("req4 doGet ---> value = " + req.getAttribute("key_req"));}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {super.doPost(req, resp);}
}

访问http://localhost:8080/tomcat-demo/req3后
日志输出

req3 doGet ---> 
req4 doGet ---> value = value from req3

2 Response

2.1 Response设置响应数据

1 设置响应行

resp.setStatus(200);

2 设置响应头

resp.setHeader("Content-type", "text/json")

3 设置响应体

getWritter();
getOutPutStream();

2.2 Response请求重定向

定义两个Servlet

@WebServlet("/resp1")
public class ResponseDemo1 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {resp.setStatus(302);resp.setHeader("location", "/tomcat-demo/resp2");System.out.println("Resp1 doGet() ");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doGet(req, resp);}
}

@WebServlet("/resp2")
public class ResponseDemo2 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {resp.setStatus(200);System.out.println("Resp2 doGet() ");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {super.doPost(req, resp);}
}

请求地址
ocalhost:8080/tomcat-demo/resp1
日志打印

Resp1 doGet() 
Resp2 doGet() 

2.3 路径问题

重定向时

resp.setHeader("location", "/tomcat-demo/resp2");

转发时

req.getRequestDispatcher("/req4").forward(req, resp);

问题: 为什么转发是不需要加路径？
转发是相对于相对于服务端，重定向时相对于浏览器。

2.4 Response响应字符数据

@WebServlet("/resp1")
public class ResponseDemo1 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {resp.setContentType("text/html, charset=utf-8");PrintWriter writer = resp.getWriter();writer.write("hello");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doGet(req, resp);}
}

2.5 Response响应字节数据

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//响应字节数据FileInputStream stream = new FileInputStream("/Users/yl/Desktop/image.png");ServletOutputStream os = resp.getOutputStream();byte[] buff = new byte[1024];int len = 0;while ((len = stream.read(buff)) != -1) {os.write(buff, 0, len);}stream.close();
}

使用工具类简化形式
添加依赖

 commons-io commons-io2.6

@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//响应字节数据FileInputStream stream = new FileInputStream("/Users/yl/Desktop/image.png");ServletOutputStream os = resp.getOutputStream();//简化方式IOUtils.copy(stream, os);stream.close();}

3 示例

3.1 登录示例

3.1.1 登录页面

LOGIN IN
Username:
Password:
   没有账号？点击注册

3.1.2 添加依赖

在pom中添加mysql和mybatis依赖

mysqlmysql-connector-java5.1.46
org.mybatismybatis3.5.5 

3.1.3 mybatis-config.xml配置

在resources目录下添加mybatis-config.xml配置
文件内容

3.1.4 创建servlet实现类

@WebServlet(urlPatterns = "/loginServlet")
public class LoginServlet extends HttpServlet {private String TAG = getClass().getSimpleName();@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println(TAG + ": doGet() ---> ");String username = req.getParameter("username");String password = req.getParameter("password");String resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);SqlSession sqlSession = sqlSessionFactory.openSession();UserMapper userMapper = sqlSession.getMapper(UserMapper.class);User user = userMapper.select(username, password);sqlSession.close();resp.setContentType("text/html;charset=utf-8");PrintWriter writer = resp.getWriter();if (user != null) {writer.write("登录成功");} else {writer.write("登录失败");}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println(TAG + ": doPost() ---> ");this.doGet(req, resp);}
}

3.1.5 添加mybatis查询语句

public interface UserMapper {@Select("select * from tb_user where username = #{username} and password= #{password}")User select(@Param("username") String username, @Param("password") String password);
}

3.1.6 mysql添加测试数据

//tb_user表
mysql> desc tb_user;
+----------+-------------+------+-----+---------+----------------+
| Field    | Type        | Null | Key | Default | Extra          |
+----------+-------------+------+-----+---------+----------------+
| id       | int(11)     | NO   | PRI | NULL    | auto_increment |
| username | varchar(20) | YES  |     | NULL    |                |
| password | varchar(20) | YES  |     | NULL    |                |
| gender   | char(1)     | YES  |     | NULL    |                |
| addr     | varchar(30) | YES  |     | NULL    |                |
+----------+-------------+------+-----+---------+----------------+//添加测试数据
mysql> insert into tb_user(username, password) values('zhangsan', '123'), ('lisi', '125');
Query OK, 2 rows affected (0.03 sec)
Records: 2  Duplicates: 0  Warnings: 0

3.1.5 测试请求

请求地址: http://localhost:8080/tomcat-demo/login.html
当username与pwd输入正确的用户名和密码时，提示登录成功

3.2 注册示例

3.2.1 注册页面

欢迎注册
已有帐号？ 登录
用户名

用户名不太受欢迎
密码

密码格式有误

3.2.2 注册Servlet

@WebServlet(urlPatterns = "/registerServlet")
public class RegisterServlet extends HttpServlet {private String TAG = getClass().getSimpleName();@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println(TAG + ": doGet() ---> ");//请求数据String username = req.getParameter("username");String password = req.getParameter("password");username = new String(username.getBytes("ISO-8859-1"), "UTF-8");User userRegister = new User();userRegister.setUsername(username);userRegister.setPassword(password);//创建UserMapperString resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);SqlSession sqlSession = sqlSessionFactory.openSession();UserMapper userMapper = sqlSession.getMapper(UserMapper.class);//查询本地user是否存在User user = userMapper.selectByUsername(username);resp.setContentType("text/html;charset=utf-8");if (user == null) {userMapper.add(userRegister);sqlSession.commit();sqlSession.close();resp.getWriter().write("注册成功!");} else {resp.getWriter().write("用户名已存在!");}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println(TAG + ": doPost() ---> ");this.doGet(req, resp);}
}

3.2.3 sql语句

public interface UserMapper {@Select("select * from tb_user where username = #{username} and password= #{password}")User select(@Param("username") String username, @Param("password") String password);@Insert("insert into tb_user values(null, #{username}, #{password}, null, null)")void add(User user);@Select("select * from tb_user where username = #{username}")User selectByUsername(String username);
}

3.2.4 测试请求

请求http://localhost:8080/tomcat-demo/register.html地址后
输入用户名和密码，当musql中不存在此用户名时，即可注册成功