WebServlet的使用

用于实现对数据库中的数据进行访问并获取,将获取的数据转化成JSON数组

引入TomCat

链接数据库配置JDBCUntil

//mysql 5 和  8
//连接数据库四要素有没有变化？
//driver   5  com.mysql.jdbc.Driver  8 com.mysql.cj.jdbc.Driver
//url      5  可以不加任何参数       8 有的需要添加时区。 shanghai
//username  root
//password  root
private static String driver="com.mysql.jdbc.Driver";
private static String url="jdbc:mysql://localhost:3306/pokemon?useSSL=false";
private static String username="root";
private static String password="justin";

static { //只会执行一次。

    try {
        //直接进行类加载 加载驱动 只需要加载一次。
        Class.forName(driver);
    } catch (ClassNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}
//工厂模式 创建一个方法获取链接对象
public static Connection getConnection() throws SQLException{
return DriverManager.getConnection(url,username,password);
}

Servlet项目创建

创建实体类

使用lombok可以简化shux

   <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.20</version>
        </dependency>

实体类对象

@Data
public class Fication {
    private String classfication;
    private Integer pokemon_count;
}

创建DAO包

public interface GoodsDAO {
    //传说级宝可梦的六种属性值
    public List<Goods> findattackTop5() throws SQLException;
    //各个世代的宝可梦数量
    public List<pokecount> findpokemon() throws SQLException;
    //所有宝可梦的身高体重属性
    public  List<shuxin> findAll() throws  SQLException;
    //宝可梦为男性的概率
    public  List<Male> findsex() throws  SQLException;
    //宝可梦各个主属性的数量
    public  List<Type> findtype() throws  SQLException;
    //宝可梦捕捉概率和种族值
    public  List<Capture> findRate() throws  SQLException;
    //宝可梦的精灵类型
    public List<Fication> findFaction() throws SQLException;
}

dao的实现类

public class GoodsDAOImpl implements GoodsDAO {

    private Connection conn=null;

    @Override
    public List<Goods> findattackTop5() throws SQLException {
        // 获取数据库连接
        this.conn= DButil.getConnection();
// 查询数据库中 pokecount 表中的数据并返回
        return DButil.queryList(this.conn, Goods.class, "select * from legendary order by rand () limit 5 ");
    }

    @Override
    public List<pokecount> findpokemon() throws SQLException {
        this.conn= DButil.getConnection();

        return DButil.queryList(this.conn, pokecount.class, "select * from pokecount");
    }

    @Override
    public List<shuxin> findAll() throws SQLException {
        this.conn= DButil.getConnection();

        return DButil.queryList(this.conn, shuxin.class, "select * from pokeshuxin");
    }

    @Override
    public List<Male> findsex() throws SQLException {
        this.conn= DButil.getConnection();

        return DButil.queryList(this.conn, Male.class, "select * from male");
    }

    @Override
    public List<Type> findtype() throws SQLException {
        this.conn= DButil.getConnection();

        return DButil.queryList(this.conn, Type.class, "select * from type");
    }

    @Override
    public List<Capture> findRate() throws SQLException {
        this.conn=DButil.getConnection();
        return DButil.queryList(this.conn,Capture.class,"select * from rate ORDER BY rand() LIMIT 10;");
    }

    @Override
    public List<Fication> findFaction() throws SQLException {
        this.conn=DButil.getConnection();

        return DButil.queryList(this.conn,Fication.class,"select * from faction ORDER BY rand() LIMIT 6");
    }
}

创建services包

接口代码和dao包一样
service的实现类

public class GoodsServiceImpl  implements GoodsService {
    private GoodsDAO goodsDAO=new GoodsDAOImpl();
    @Override
    public List<Goods> findattackTop5() throws SQLException {

        return goodsDAO.findattackTop5();
    }

    @Override
    public List<pokecount> findpokemon() throws SQLException {
        return  goodsDAO.findpokemon();
    }

    @Override
    public List<shuxin> findAll() throws SQLException {
        return goodsDAO.findAll();
    }

    @Override
    public List<Male> findMale() throws SQLException {
        return goodsDAO.findsex();
    }

    @Override
    public List<Type> findType() throws SQLException {
        return goodsDAO.findtype();
    }

    @Override
    public List<Capture> findRate() throws SQLException {
        return goodsDAO.findRate();
    }

    @Override
    public List<Fication> findFaction() throws SQLException {
        return goodsDAO.findFaction();
    }


}

创建Controller包

将获取的数据库数据转化成JSON数组
pom.xml中导入json包

<dependency>
  <groupId>com.alibaba</groupId>
  <artifactId>fastjson</artifactId>
  <version>1.2.37</version>
</dependency>

创建Controller类

// 使用@WebServlet注解指定Servlet的URL映射
@WebServlet("/findtop.do")
public class FandGoodsServlet extends HttpServlet {
    
    // 创建GoodsService对象并初始化
    private GoodsService goodsService = new GoodsServiceImpl();

    // 处理HTTP GET请求
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        List<Goods> all = null;
        try {
            // 调用goodsService的findattackTop5方法来获取数据
            all = goodsService.findattackTop5();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        
        // 将获取到的数据转换成JSON字符串
        String s = JSON.toJSONString(all);
        
        // 在控制台打印JSON字符串
        System.out.println("s = " + s);
        
        // 将JSON字符串写入HTTP响应
        resp.getWriter().write(s);
    }
}