有效沟通问答-【官方】百战程序员_IT在线教育培训机构

 create table departments(department_id int,dapartment_name varchar(30) unique,location_id int not null,constraint dept_pk primary key(department_id) auto_increment(department));

自动增长可以在最后定义吗我这么写不对啊

JAVA 全系列/第三阶段：数据库编程/MySQL数据库的使用 29837楼

这啥意思怎么解决呢

JAVA 全系列/第三阶段：数据库编程/MySQL数据库的使用 29838楼

老师你好，请问转换后发生乱码怎么处理呢？

import struct
from socket import *
filename = 'zzbds.azw3'
server_ip = '100.98.57.142'
send_data = struct.pack('!H%dsb5sb' % len(filename), 1, filename.encode(), 0, 'octet'.encode(), 0)
s = socket(AF_INET, SOCK_DGRAM)
s.sendto(send_data, (server_ip, 69))
f = open('f:\\1\\a.txt', 'ab')    # a代表以追加模式打开，b代表以二进制模式打开  'f:\1\a.png'

while True:
    recv_data = s.recvfrom(2048)    # 接受数据
    caozuoma, ack_num = struct.unpack('!HH', recv_data[0][:4])  # 获取数据模块
    rand_port = recv_data[1][1]     # 随机获取服务器端口
    if int(caozuoma) == 5:
        print('文件不存在...')
        break
    print("操作码: %d, ACK: %d, 服务器随机端口：%d,数据长度: %d" % (caozuoma, ack_num, rand_port, len(recv_data[0])))
    f.write(recv_data[0][4:])   # 将数据写入
    if len(recv_data[0]) < 516:
        break
    ack_data = struct.pack("!HH", 4, ack_num)
    s.sendto(ack_data, (server_ip, rand_port))  # 回复ACK确认包

Python 全系列/第三阶段：Python 网络与并发编程/网络通信 29839楼

const express = require('express');

const app = express();

app.get("/",(req,res)=>{

res.send({

msg:'success'

})

app.listen(3003,function(){

console.log('服务器运行在3003端口');

})

WEB前端全系列/第二十阶段：Vue2企业级项目（旧）/Ego商城高级Vue实战项目 29840楼

public class User {
    int id; // id
    String name; //账户名
    String pwd; //密码

    public User(){
    }

    public User(int id,String name){
        super();
        this.id = id; 
        this.name = name;
    }

    public User(int id,String name,String pwd){
        this.id = id;
        this.name = name;
        this.pwd = pwd;
        System.out.println(id);
        System.out.println(name);
        System.out.println(pwd);
    }

    public static void main(String[] args) {
        User u1 = new User();
        User u2 = new User(1001,"张三");
        User u3 = new User(1002,"李四","qweqe");
        System.out.println("use1:"+u1);
        System.out.println("use2:"+u2);
        System.out.println("use3:"+u3);

    }


}

输出：

1002

李四

qweqe

use1:User@7291c18f

use2:User@34a245ab

use3:User@7cc355be

问题1 ：为什么上面id、name、pwd可以输出我赋值后的内容。顺序没有影响吗？

问题2：u1、u2、u3则输出的不是我赋值的内容

问题3：

public User(int id,String name){
        super();
        this.id = id; 
        this.name = name;
    }

为什么在这里要输入super(); 它的作用是什么？

JAVA 全系列/第一阶段：JAVA 快速入门/面向对象详解和JVM底层内存分析 29841楼

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    div {
        width: 30px;
        height: 30px;
        background-color: pink;
        position: absolute;
        line-height: 15px;
        text-align: center;
    }
</style>

<body>
    <input type="range" min="0" max="100" value="50">
    <div id="box"></div>

    <script>

        var input = document.querySelector("input")
        var div = document.getElementById('box');
        var flag = false;
        input.onmousedown = function () {
            console.log("(x,y):(" + event.clientX + "," + event.clientY + ")");
        }

    </script>
</body>

</html>

老师，我是什么步骤错了，鼠标事件一直没效果，是没获取到input吗

WEB前端全系列/第二阶段：JavaScript编程模块/浏览器模型(BOM) 29842楼

在启动start.bat报错:

Java HotSpot(TM) 64-Bit Server VM warning: Ignoring option MaxPermSize; support was removed in 8.0

log4j:WARN No appenders could be found for logger (com.alibaba.dubbo.common.logger.LoggerFactory).

log4j:WARN Please initialize the log4j system properly.

log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.alibaba.dubbo.monitor.MonitorService': Instantiation of bean failed; nested exception is java.lang.ExceptionInInitializerError

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:883)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:839)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:440)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409)

at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380)

at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264)

at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)

at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261)

at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185)

at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164)

at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeansOfType(DefaultListableBeanFactory.java:308)

at org.springframework.context.support.AbstractApplicationContext.getBeansOfType(AbstractApplicationContext.java:947)

at org.springframework.context.support.AbstractApplicationContext.registerListeners(AbstractApplicationContext.java:701)

at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:377)

at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)

at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:93)

at com.alibaba.dubbo.container.spring.SpringContainer.start(SpringContainer.java:50)

at com.alibaba.dubbo.container.Main.main(Main.java:80)

Caused by: java.lang.ExceptionInInitializerError

at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)

at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)

at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)

at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)

at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:100)

at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:61)

at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:877)

... 18 more

Caused by: java.lang.IllegalStateException: fail to create adaptive instance: java.lang.IllegalStateException: Can not create adaptive extenstion interface com.alibaba.dubbo.rpc.Protocol, cause: java.io.IOException: invalid constant type: 18

at com.alibaba.dubbo.common.extension.ExtensionLoader.getAdaptiveExtension(ExtensionLoader.java:459)

at com.alibaba.dubbo.config.ServiceConfig.<clinit>(ServiceConfig.java:60)

... 26 more

Caused by: java.lang.IllegalStateException: Can not create adaptive extenstion interface com.alibaba.dubbo.rpc.Protocol, cause: java.io.IOException: invalid constant type: 18

at com.alibaba.dubbo.common.extension.ExtensionLoader.createAdaptiveExtension(ExtensionLoader.java:723)

at com.alibaba.dubbo.common.extension.ExtensionLoader.getAdaptiveExtension(ExtensionLoader.java:455)

... 27 more

Caused by: java.lang.RuntimeException: java.io.IOException: invalid constant type: 18

at javassist.CtClassType.getClassFile2(CtClassType.java:204)

at javassist.CtClassType.subtypeOf(CtClassType.java:304)

at javassist.compiler.MemberResolver.compareSignature(MemberResolver.java:248)

at javassist.compiler.MemberResolver.lookupMethod(MemberResolver.java:120)

at javassist.compiler.MemberResolver.lookupMethod(MemberResolver.java:97)

at javassist.compiler.MemberCodeGen.atMethodCallCore(MemberCodeGen.java:562)

at javassist.compiler.MemberCodeGen.atCallExpr(MemberCodeGen.java:524)

at javassist.compiler.JvstCodeGen.atCallExpr(JvstCodeGen.java:244)

at javassist.compiler.ast.CallExpr.accept(CallExpr.java:46)

at javassist.compiler.MemberCodeGen.atCallExpr(MemberCodeGen.java:497)

at javassist.compiler.JvstCodeGen.atCallExpr(JvstCodeGen.java:244)

at javassist.compiler.ast.CallExpr.accept(CallExpr.java:46)

at javassist.compiler.MemberCodeGen.atCallExpr(MemberCodeGen.java:497)

at javassist.compiler.JvstCodeGen.atCallExpr(JvstCodeGen.java:244)

at javassist.compiler.ast.CallExpr.accept(CallExpr.java:46)

at javassist.compiler.MemberCodeGen.atCallExpr(MemberCodeGen.java:497)

at javassist.compiler.JvstCodeGen.atCallExpr(JvstCodeGen.java:244)

at javassist.compiler.ast.CallExpr.accept(CallExpr.java:46)

at javassist.compiler.CodeGen.atBinExpr(CodeGen.java:964)

at javassist.compiler.ast.BinExpr.accept(BinExpr.java:41)

at javassist.compiler.JvstCodeGen.atMethodArgs(JvstCodeGen.java:358)

at javassist.compiler.MemberCodeGen.atMethodCallCore(MemberCodeGen.java:556)

at javassist.compiler.MemberCodeGen.atNewExpr(MemberCodeGen.java:302)

at javassist.compiler.ast.NewExpr.accept(NewExpr.java:73)

at javassist.compiler.CodeGen.compileExpr(CodeGen.java:230)

at javassist.compiler.CodeGen.atThrowStmnt(CodeGen.java:628)

at javassist.compiler.CodeGen.atStmnt(CodeGen.java:365)

at javassist.compiler.ast.Stmnt.accept(Stmnt.java:50)

at javassist.compiler.CodeGen.atIfStmnt(CodeGen.java:391)

at javassist.compiler.CodeGen.atStmnt(CodeGen.java:355)

at javassist.compiler.ast.Stmnt.accept(Stmnt.java:50)

at javassist.compiler.CodeGen.atStmnt(CodeGen.java:351)

at javassist.compiler.ast.Stmnt.accept(Stmnt.java:50)

at javassist.compiler.CodeGen.atMethodBody(CodeGen.java:292)

at javassist.compiler.CodeGen.atMethodDecl(CodeGen.java:274)

at javassist.compiler.ast.MethodDecl.accept(MethodDecl.java:44)

at javassist.compiler.Javac.compileMethod(Javac.java:169)

at javassist.compiler.Javac.compile(Javac.java:95)

at javassist.CtNewMethod.make(CtNewMethod.java:74)

at javassist.CtNewMethod.make(CtNewMethod.java:45)

at com.alibaba.dubbo.common.compiler.support.JavassistCompiler.doCompile(JavassistCompiler.java:119)

at com.alibaba.dubbo.common.compiler.support.AbstractCompiler.compile(AbstractCompiler.java:59)

at com.alibaba.dubbo.common.compiler.support.AdaptiveCompiler.compile(AdaptiveCompiler.java:46)

at com.alibaba.dubbo.common.extension.ExtensionLoader.createAdaptiveExtensionClass(ExtensionLoader.java:739)

at com.alibaba.dubbo.common.extension.ExtensionLoader.getAdaptiveExtensionClass(ExtensionLoader.java:732)

at com.alibaba.dubbo.common.extension.ExtensionLoader.createAdaptiveExtension(ExtensionLoader.java:721)

... 28 more

Caused by: java.io.IOException: invalid constant type: 18

at javassist.bytecode.ConstPool.readOne(ConstPool.java:1113)

at javassist.bytecode.ConstPool.read(ConstPool.java:1056)

at javassist.bytecode.ConstPool.<init>(ConstPool.java:150)

at javassist.bytecode.ClassFile.read(ClassFile.java:765)

at javassist.bytecode.ClassFile.<init>(ClassFile.java:109)

at javassist.CtClassType.getClassFile2(CtClassType.java:191)

... 73 more

请按任意键继续. . .

JAVA 全系列/第十一阶段：分布式RPC调用和分布式文件存储/Dubbo 29843楼

老师我把

c = test01()

这个C是代表的什么意思？好像打印出来和c=test01 数值不一样。

Python 全系列/第一阶段：Python入门/函数和内存分析 29844楼

time
time.clock()
list1 = [x x (,,)]
costTime = time.clock()
(%costTime)
list2 = [x x (,) x % == ]
(list2)
list3 = [a + b a b ]
(list3)

Python 全系列/第四阶段：函数式编程和核心特性/生成器和装饰器 29845楼

1.png

为啥画圈的以下都没有出来结果啊

Python 全系列/第二阶段：Python 深入与提高/文件处理 29846楼

1.png

为什么代码运行完没有出现gg的压缩文件啊

Python 全系列/第二阶段：Python 深入与提高/文件处理 29847楼

老师，我有2个问题，麻烦帮忙解答，谢谢！

如何实现爬虫过程中将数据从redis中保存到mongo中,或者自动实现爬取结束后数据从redis中转移到mongo中，而不是再手动运行一个.py文件从redis中导出数据到mongo中
如何将数据从redis或mongo中导出到本地文件。

Python 全系列/第十五阶段：Python 爬虫开发/分布式爬虫 29848楼

老师这个使用insertBefore执行不了

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<script>
			
			function addNode(){
			//获得表单对象
			var fo =document.getElementById("fom");
			
			//创建节点的方法
			var p =	document.createElement("p");
			p.innerText = "照片";
			
			var inp =document.createElement("input");
			inp.type="file";
			
			var inp2 = document.createElement("input");
			inp2.type = "button";
			inp2.value = "删除";
			
			inp2.onclick =function(){
				//移除子节点
				p.removeChild(inp);
				p.removeChild(inp2);
				//移除本身
				p.remove();
			}
			
				//添加节点对象 添加到了最后
			   //fo.appendChild(p);
				
				//获得最后一个节点对象
				var la =document.getElementById("las");
				// 在指定元素之前添加节点
				fo.insertBefore("p.la");
				p.appendChild(inp);
				p.appendChild(inp2);
			}
			
		</script>
	</head>
	<body>
		
		<form id="fom">
			
			<p>
				用户名:<input type="text" />
			</p>
			
			
			<p>
				照片:<input type="file" />
				<input type="button" value="添加" onclick="addNode()"/>
			</p>
			
			
			<p id="las">
				<input type="button" name="" id="" value="提交" />
				<input type="button" name="" id="" value="清空" />
			</p>
		</form>
		
	</body>
</html>

错误提示

JAVA 全系列/第四阶段：网页编程和设计/Javascript 语言（旧） 29849楼

老师，分布式的3种写法中，我怎么感觉第一种写法要修改的代码最少，最容易理解，执行效率最高，不需要麻烦的手动lpush操作。其次是第二种写法。至于第三种写法，我怎么感觉crawlspider的方式并不比spider好用

Python 全系列/第十五阶段：Python 爬虫开发/分布式爬虫 29850楼

同学您好