第九章 从0-1搭建一个简单的JavaWeb系统（一）

已于 2024-09-23 11:02:00 修改
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分类专栏： JavaWeb基础知识 文章标签： python 前端 开发语言
于 2024-09-23 09:49:47 首次发布
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本文链接：https://blog.youkuaiyun.com/qushaming/article/details/142449718
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目录

一、创建工程

二、创建路径包

三、编写代码

3.1. BaseDao

3.2. 编写字符编码过滤器 

3.3. 编写业务实体对象 

3.4. 编写数据库配置文件

3.5. 编写web.xml 

四、未完待续

本章节的每一段代码，建议全部自己敲一遍，加深印象，切勿直接复制黏贴。

完整工程资源文件夸克网盘下载地址：

链接：https://pan.quark.cn/s/9766fe029b27

一、创建工程

二、创建路径包

创建好工程后，按照下图所示建立好对应的路径包：

三、编写代码

pom.xml依赖

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>org.example</groupId>
  <artifactId>smbms</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>war</packaging>

  <name>smbms Maven Webapp</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>8</maven.compiler.source>
    <maven.compiler.target>8</maven.compiler.target>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.13.1</version>
    </dependency>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>servlet-api</artifactId>
      <version>2.5</version>
    </dependency>
    <dependency>
      <groupId>javax.servlet.jsp</groupId>
      <artifactId>jsp-api</artifactId>
      <version>2.1</version>
    </dependency>
    <dependency>
      <groupId>org.glassfish.web</groupId>
      <artifactId>javax.servlet.jsp.jstl</artifactId>
      <version>1.2.5</version>
    </dependency>
    <!-- 连接数据库 -->
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>8.0.31</version>
    </dependency>
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>fastjson</artifactId>
      <version>1.2.80</version>
    </dependency>
    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <version>1.18.26  </version>
    </dependency>
  </dependencies>

  <build>
    <finalName>smbms</finalName>
    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
      <plugins>
        <plugin>
          <artifactId>maven-clean-plugin</artifactId>
          <version>3.4.0</version>
        </plugin>
        <!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
        <plugin>
          <artifactId>maven-resources-plugin</artifactId>
          <version>3.3.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.13.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-surefire-plugin</artifactId>
          <version>3.3.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-war-plugin</artifactId>
          <version>3.4.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-install-plugin</artifactId>
          <version>3.1.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-deploy-plugin</artifactId>
          <version>3.1.2</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>

3.1. BaseDao

该类用于和数据库的交互，创建/关闭数据库连接/操作增删改查的SQL

package com.example.dao;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

public class BaseDao {
    private static String driver;
    private static String url;
    private static String username;
    private static String password;

    static {
        Properties properties = new Properties();
        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");
    }

    public static Connection getConnection() {
        Connection connection = null;
        try {
            Class.forName(driver);
            connection = DriverManager.getConnection(url, username, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return connection;
    }

    public static ResultSet execute(Connection connection, String sql, Object[] params, ResultSet resultSet, PreparedStatement preparedStatement) {
        try {
            preparedStatement = connection.prepareStatement(sql);
            for (int i = 0; i < params.length; i++) {
                // setObject参数，参数占位符从1开始，我们的参数数组从0开始
                preparedStatement.setObject(i + 1, params[0]);
            }
            resultSet = preparedStatement.executeQuery();

        } catch (SQLException e) {
            e.printStackTrace();
        }
        return resultSet;
    }

    public static int execute(Connection connection, String sql, Object[] params, PreparedStatement preparedStatement) {
        int updateRows = 0;
        try {
            preparedStatement = connection.prepareStatement(sql);
            for (int i = 0; i < params.length; i++) {
                // setObject参数，参数占位符从1开始，我们的参数数组从0开始
                preparedStatement.setObject(i + 1, params[0]);
            }
            updateRows = preparedStatement.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return updateRows;
    }

    public static boolean closeResource(Connection connection, PreparedStatement preparedStatement, ResultSet resultSet) {
        boolean flag = true;
        if (resultSet != null) {
            try {
                resultSet.close();
            } catch (SQLException e) {
                e.printStackTrace();
                flag = false;
            }
        }
        if (preparedStatement != null) {
            try {
                preparedStatement.close();
            } catch (SQLException e) {
                e.printStackTrace();
                flag = false;
            }
        }
        if (connection != null) {
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
                flag = false;
            }
        }
        return flag;
    }
}

3.2. 编写字符编码过滤器 

设定字符编码为utf-8避免中文乱码，通过过滤器能统一拦截处理字符编码，因此不需要在每个Servlet中再单独进行处理，更便于管理。

package com.example.filter;

import javax.servlet.*;
import java.io.IOException;

public class CharacterEncodingFilter implements Filter {
    public void init(FilterConfig config) throws ServletException {
    }

    public void destroy() {
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setCharacterEncoding("utf-8");
        chain.doFilter(request,response);
    }
}

3.3. 编写业务实体对象 

每个实体对象对应一张相关表

package com.example.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.Date;

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Address {
    private Integer id;
    private String contact;
    private String addressDesc;
    private String postCode;
    private String tel;
    private Integer createdBy;
    private Date creationDate;
    private Integer modifyBy;
    private Date modifyDate;
    private Integer userId;
}

package com.example.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.math.BigDecimal;
import java.util.Date;

@NoArgsConstructor
@AllArgsConstructor
@Data
public class Bill {
    private Integer id;
    private String billCode;
    private String productName;
    private String productDesc;
    private String productUnit;
    private BigDecimal productCount;
    private BigDecimal totalPrice;
    private Integer isPayment;
    private Integer createdBy;
    private Date creationDate;
    private Integer modifyBy;
    private Date modifyDate;
    private Integer providerId;
}

package com.example.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.Date;

@AllArgsConstructor
@NoArgsConstructor
@Data
public class Provider {
    private Integer id;
    private String proCode;
    private String proName;
    private String proDesc;
    private String proContact;
    private String proPhone;
    private String proAddress;
    private String proFax;
    private Integer createdBy;
    private Date creationDate;
    private Date modifyDate;
    private Integer modifyBy;
}

package com.example.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.util.Date;

@NoArgsConstructor
@AllArgsConstructor
@Data
public class Role {
    private Integer id;
    private String roleCode;
    private String roleName;
    private Integer createdBy;
    private Date creationDate;
    private Integer modifyBy;
    private Date modifyDate;
}

package com.example.pojo;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

import java.util.Date;

@AllArgsConstructor
@NoArgsConstructor
@Data
public class User {
    private Integer id;
    private String userCode;
    private String userName;
    private String userPassword;
    private Integer gender;
    private Date birthday;
    private String phone;
    private String address;
    private Integer userRole;
    private Integer createdBy;
    private Date creationDate;
    private Integer modifyBy;
    private Date modifyDate;
    private Integer age;

    public Integer getAge() {
        Date date = new Date();
        return date.getYear() - birthday.getYear();
    }
}

3.4. 编写数据库配置文件

 在db.properties中配置数据库连接信息

# MySQL驱动 8之前的版本com.mysql.jdbc.Driver 我本地用的8
driver=com.mysql.cj.jdbc.Driver
# 数据库连接地址
url=jdbc:mysql://localhost:3306/smbms/useSSl=true&useUnicode=true&characterEncoding=utf-8
# 用户名
username=root
# 密码
password=Wangzhexiao3313@

3.5. 编写web.xml 

<?xml version="1.0" encoding="UTF-8"?>
<web-app
    version="4.0"
    xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    xmlns:javaee="http://xmlns.jcp.org/xml/ns/javaee"
    xmlns:xml="http://www.w3.org/XML/1998/namespace"
    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">
  <display-name>Archetype Created Web Application</display-name>
    <filter>
        <filter-name>CharacterEncodingFilter</filter-name>
        <filter-class>com.example.filter.CharacterEncodingFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>CharacterEncodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>

四、未完待续

后续内容请查阅下一章节，待更中……

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