第一步：
修改xml：
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0" metadata-complete="true">
</web-app>第二步：配置Tomcat
<body>
hello world,tomcat
</body>
第三步：测试项目是否能跑起来。自己加个helloworld
第四步：导入依赖
jsp,Servlet,mysqlconnect
<!--导入包-->
<dependencies>
<!--servlet-->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>2.5</version>
</dependency>
<!--servlet-->
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>javax.servlet.jsp-api</artifactId>
<version>2.3.3</version>
</dependency>
<!--mysql-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.47</version>
</dependency>
<!--jstl-->
<dependency>
<groupId>javax.servlet.jsp.jstl</groupId>
<artifactId>jstl-api</artifactId>
<version>1.2</version>
</dependency>
<!--standard-->
<dependency>
<groupId>taglibs</groupId>
<artifactId>standard</artifactId>
<version>1.1.2</version>
</dependency>
</dependencies>
<!-- 在build中配置resources ， 来防止我们资源导出失败的问题-->
<build>
<resources>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
</resource>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
</resource>
</resources>
</build>
第五步：创建项目包，结构，MVC
第六步：编写实体类
ORM映射，表--类--映射
第七步：编写基础公共类
db.properites
7.1数据库配置文件
7.2编写数据库，公共类，在不使用框架的情况下
package com.xuwen.dao;
import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;
/**
* author:xuwen
* Created on 2021/7/20
*/
//操作数据库的基本类
public class BaseDao {
private static String driver;
private static String url;
private static String username;
private static String password;
//static静态代码块，类加载的时候，就初始化
static{
Properties properties = new Properties();
//通过类加载器，读取对应的资源
InputStream is = BaseDao.class.getClassLoader().getResourceAsStream("db.properties");
try {
properties.load(is);
} catch (IOException e) {
e.printStackTrace();
}
driver = properties.getProperty("driver");
url = properties.getProperty("url");
username = properties.getProperty("username");
password = properties.getProperty("password");
}
//获得数据库连接
public static Connection getConnection(){
Connection connection = null;
try {
Class.forName(driver);
connection = DriverManager.getConnection(url,username,password);
} catch (Exception e) {
e.printStackTrace();
}
return connection;
}
//编写查询公共类
public static ResultSet execute(Connection connection, String sql, Object[] params,ResultSet resultSet,PreparedStatement preparedStatement) throws SQLException {
//预编译的sql在后面执行，就可以了
preparedStatement = connection.prepareStatement(sql);
for (int i=0;i<params.length;i++){
preparedStatement.setObject(i+1,params[i]);
}
resultSet = preparedStatement.executeQuery();
return resultSet;
}
//编写增，删，改，公共类
public static int execute(Connection connection, String sql, Object[] params,PreparedStatement preparedStatement) throws SQLException {
preparedStatement = connection.prepareStatement(sql);
for (int i=0;i<params.length;i++){
preparedStatement.setObject(i+1,params[i]);
}
int updateRows = preparedStatement.executeUpdate();
return updateRows;
}
//释放连接
public static boolean closeResource(Connection connection, PreparedStatement preparedStatement, ResultSet resultSet){
boolean flag = true;
if(resultSet != null){
try {
resultSet.close();
//GC回收
resultSet = null;
} catch (SQLException e) {
e.printStackTrace();
flag = false;
}
}
if(connection != null){
try {
connection.close();
//GC回收
connection = null;
} catch (SQLException e) {
e.printStackTrace();
flag = false;
}
}
if(preparedStatement != null){
try {
preparedStatement.close();
//GC回收
preparedStatement = null;
} catch (SQLException e) {
e.printStackTrace();
flag = false;
}
}
return flag;
}
}7.3过滤器filter,注意不要倒错Filter的包
package com.xuwen.filter;
import javax.servlet.*;
import java.io.IOException;
import java.util.logging.LogRecord;
/**
* author:xuwen
* Created on 2021/7/20
*/
public class CharacterEncodingFilter implements Filter {
public void init(FilterConfig filterConfig) throws ServletException {
}
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
servletRequest.setCharacterEncoding("utf-8");
servletResponse.setCharacterEncoding("utf-8");
filterChain.doFilter(servletRequest,servletResponse);
}
public void destroy() {
}
}
7.4 xml
<!--字符编码过滤器-->
<filter>
<filter-name>CharacterEncodingFilter</filter-name>
<filter-class>com.xuwen.filter.CharacterEncodingFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>CharacterEncodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>