项目实战：添加库存时判断水果名称是否已经存在

1、在add.html页面绑定键盘按键松开事情onkeyup

    
    
    
    
    
    



    

        
添加水果库存信息
    
    

        

            

                
名称:
                
 
            
            

                
单价:
                
 
            
            

                
库存:
                
 
            
            

                
备注:
                
 
            
            

                

                    
                    
                
            
        
    

2、在add.js中添加checkFname函数

2.1、common.js

function $(key){
    if(key){
        if(key.startsWith("#")){
            key = key.substring(1)
            return document.getElementById(key)
        }else{
            let nodeList = document.getElementsByName(key)
            return Array.from(nodeList)
        }
    }
}

function add(){
    let fname = $("#fname").value
    let price = $("#price").value
    let fcount = $("#fcount").value
    let remark = $("#remark").value

    //let fruit = {"fname":fname,"price":price,"fcount":fcount,"remark":remark}
    let fruit = {}
    fruit.fname=fname
    fruit.price = price
    fruit.fcount=fcount
    fruit.remark=remark

    axios({
        method:'post',
        url:'add',
        data:fruit
    }).then(response=>{
        if(response.data.flag){
            window.location.href='index.html'
        }
    })
}

function checkFname(fname){
    axios({
        method:'get',
        url:"getFname",
        params:{
            fname:fname
        }
    }).then(response=>{
        let fnameSpan= $("#fnameSpan");
        if(response.data.flag){
            fnameSpan.innerText = '名称可添加'
            fnameSpan.style.color='green'
        }else{
            fnameSpan.innerText = '名称已存在'
            fnameSpan.style.color='red'
        }
    })
}

3、编写Controller层GetFanemServlet

package com.csdn.fruit.servlet;
import com.csdn.fruit.dao.FruitDao;
import com.csdn.fruit.dao.impl.FruitDaoImpl;
import com.csdn.fruit.dto.Result;
import com.csdn.fruit.pojo.Fruit;
import com.csdn.fruit.util.ResponseUtil;
import jakarta.servlet.GenericServlet;
import jakarta.servlet.ServletException;
import jakarta.servlet.ServletRequest;
import jakarta.servlet.ServletResponse;
import jakarta.servlet.annotation.WebServlet;
import java.io.IOException;
@WebServlet("/getFname")
public class GetFnameServlet extends GenericServlet {
    FruitDao fruitDao = new FruitDaoImpl();
    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        String fname = servletRequest.getParameter("fname");
        Fruit fruit = fruitDao.getFruitByFname(fname);
        ResponseUtil.print(servletResponse, fruit == null ? Result.OK() : Result.Fail());
    }
}