Use Servlet to modify the fruit inventory system and use PostMan to test Servlet requests

 <packaging>war</packaging>
 <dependencies>
    <dependency>
      <groupId>jakarta.servlet</groupId>
      <artifactId>jakarta.servlet-api</artifactId>
      <version>6.0.0</version>
    </dependency>

    <dependency>
      <groupId>com.csdn</groupId>
      <artifactId>pro03-fruit-optimize</artifactId>
      <version>1.0-SNAPSHOT</version>
    </dependency>
 </dependencies>

• pro03-fruit-optimize is a jar package packaged by myself. Its function is to realize the addition, deletion, modification and check of the fruit system

1. Query fruit list IndexServlet

package com.csdn.fruit.servlet;
import com.csdn.fruit.dao.FruitDao;
import com.csdn.fruit.dao.impl.FruitDaoImpl;
import com.csdn.fruit.pojo.Fruit;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;
@WebServlet("/index")
public class IndexServlet extends HttpServlet {

    private FruitDao fruitDao = new FruitDaoImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        List<Fruit> fruitList = fruitDao.getFruitList();
        fruitList.stream().forEach(System.out::println);
    }
}

• The FruitDao fruit data access object interface and FruitDaoImpl fruit data access object implementation class are all in the pro03-fruit-optimize jar package

2. Query fruit EditServlet by fruit name

package com.csdn.fruit.servlet;
import com.csdn.fruit.dao.FruitDao;
import com.csdn.fruit.dao.impl.FruitDaoImpl;
import com.csdn.fruit.pojo.Fruit;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/edit")
public class EditServlet extends HttpServlet {

    FruitDao fruitDao = new FruitDaoImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String fname = req.getParameter("fname");
        Fruit fruit = fruitDao.getFruitByFname(fname);
        System.out.println(fruit);
    }
}

3. Modify inventory according to fruit name UpdateServlet

package com.csdn.fruit.servlet;
import com.csdn.fruit.dao.FruitDao;
import com.csdn.fruit.dao.impl.FruitDaoImpl;
import com.csdn.fruit.pojo.Fruit;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/update")
public class UpdateServlet extends HttpServlet {

    private FruitDao fruitDao = new FruitDaoImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //String fidStr = req.getParameter("fid");
        //Integer fid = Integer.parseInt(fidStr);
        String fname = req.getParameter("fname");
        //Integer price = Integer.parseInt(req.getParameter("price"));
        Integer fcount = Integer.parseInt(req.getParameter("fcount"));
        //String remark = req.getParameter("remark");

        fruitDao.updateFruit(new Fruit(0,fname, 0, fcount, null));
        System.out.println("Modification successful");
    }
}

• Because my bottom layer, FruitDaoImpl, is to modify the inventory of fruits through the fruit name, so I can only modify the inventory fcount here

• <strong>String sql = "update t_fruit set fcount=? where fname = ?";</strong>

4. Delete fruit records DelServlet based on fruit name

package com.csdn.fruit.servlet;
import com.csdn.fruit.dao.FruitDao;
import com.csdn.fruit.dao.impl.FruitDaoImpl;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/del")
public class DelServlet extends HttpServlet {

    FruitDao fruitDao = new FruitDaoImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String fname = req.getParameter("fname");
        fruitDao.delFruit(fname);
        System.out.println("Deletion successful!");

    }
}

5. Add fruit AddServlet

package com.csdn.fruit.servlet;
import com.csdn.fruit.dao.FruitDao;
import com.csdn.fruit.dao.impl.FruitDaoImpl;
import com.csdn.fruit.pojo.Fruit;
import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/add")
public class AddServlet extends HttpServlet {

    private FruitDao fruitDao = new FruitDaoImpl();

    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String fname = req.getParameter("fname");
        Integer price = Integer.parseInt(req.getParameter("price"));
        Integer fcount = Integer.parseInt(req.getParameter("fcount"));
        String remark = req.getParameter("remark");

        Fruit fruit = new Fruit(fname, price, fcount, remark);
        fruitDao.addFruit(fruit);

        System.out.println("Added successfully!");
    }
}

• Note: In the Post request here, the value of enctype must be adjusted to x-www-form-urlencoded

6. Query string (query string)

1. In an HTTP GET request, the query string is the part after the question mark (?) in the URL and is used to pass parameters to the server. The format of the query string usually consists of key-value pairs. Keys and values are connected using the equal sign (=), and different key-value pairs are connected using the ampersand (&).
2. For example, here is an example URL containing a query string:

3. https://example.com/api/users?name=John & amp;age=30

4. In this example, the query string is name=John & amp;age=30. It contains two key-value pairs, namely name=John and age=30.
5. In Java’s java.net.URI class, you can use the getRawQuery() method to obtain the original query string. For example:

6. URI uri = new URI("https://example.com/api/users?name=John & amp;age=30");
   String queryString = uri.getRawQuery(); // Return "name=John & amp;age=30"

7. Note that after obtaining the query string, you can use string processing methods in Java or other programming languages to parse and extract specific parameter values.

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