麻烦老师帮我看下为什么报错。

log4j:WARN No appenders could be found for logger (org.apache.ibatis.logging.LogFactory).

log4j:WARN Please initialize the log4j system properly.

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

Exception in thread "main" org.apache.ibatis.exceptions.PersistenceException: 

### Error querying database.  Cause: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: Cannot find class: com.mysql.jdbc.Driver 

### The error may exist in com/bjsxt/pojo/mapper/employee2mapper.xml

### The error may involve com.bjsxt.pojo.mapper.employee2mapper.selectall

### The error occurred while executing a query

### Cause: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: Cannot find class: com.mysql.jdbc.Driver 

at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)

at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:149)

at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:140)

at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:135)

at com.bjsxt.pojo.dao.impl.employee2impl.selectall(employee2impl.java:22)

at com.bjsxt.pojo.test.Test.main(Test.java:12)

Caused by: java.sql.SQLException: Error setting driver on UnpooledDataSource. Cause: java.lang.ClassNotFoundException: Cannot find class: com.mysql.jdbc.Driver 

at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.initializeDriver(UnpooledDataSource.java:244)

at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:223)

at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.doGetConnection(UnpooledDataSource.java:219)

at org.apache.ibatis.datasource.unpooled.UnpooledDataSource.getConnection(UnpooledDataSource.java:95)

at org.apache.ibatis.datasource.pooled.PooledDataSource.popConnection(PooledDataSource.java:432)

at org.apache.ibatis.datasource.pooled.PooledDataSource.getConnection(PooledDataSource.java:89)

at org.apache.ibatis.transaction.jdbc.JdbcTransaction.openConnection(JdbcTransaction.java:139)

at org.apache.ibatis.transaction.jdbc.JdbcTransaction.getConnection(JdbcTransaction.java:61)

at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:337)

at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:86)

at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:62)

at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:325)

at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156)

at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109)

at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:89)

at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:147)

... 4 more

Process finished with exit code 1

老师，这个浅拷贝和深拷贝，在我这个编程中怎么没有突现浅拷贝和深拷贝

#浅拷贝和深拷贝
import copy
a =[50,60,[7,9]]
b=copy.copy(a)
print("a:",a)
print("b:",b)

b.append(70)
print("000000000000")
print("a:",a)
print("b:",b)
def xell():
    a = [50, 60, [7, 9]]
    b = copy.deepcopy(a)
    print("a:", a)
    print("b:", b)

    b.append(70)
    print("1111111111111111111")
    print("a:", a)
    print("b:", b)

关于本章代码中最后两行：

s= SalaryAccount()
print(s(30000))

这里我不懂第一行的SalaryAccount后为什么要加（）

根据myoo_02.py 最后几行的代码：

stu2 = Student
s1 = Student("高淇",60)
s2 = stu2("高希希",100)

s1.say_score()
s2.say_score()

第一行中stu2 = Student是不用加（）的，

之后传参时候直接

stu2('高希希',100)

即可。

我感觉这里和上述代码实现的原理是相似的，为什么上一个代码中需要加括号？

为什么不可以写成

for(char cc = 'a',int i=0;i<26;i++){
    char cc2 = (char)(cc+i);
    System.out.println(cc2+"\t");

}

绝对路径报错了

老师能把jdk1.8发给我一下吗，一直闪退没办法了

老师，我这里出现了这个网页404错误

我用了源码 也是这样   我敲的代码都是按老师敲的  还是有这个错误

为什么设置三角形只设置了下边，左边和右边。为什么上边不设置，老师以前讲的是四个都得写，而且我也试验过不行，为什么在这里又可以，希望老师能好好解答一下。

一、图片

二、问题

1.  创建新项目，如图片所示，没有flask选项，怎么办

2. 创建虚拟环境，位置是在python官方IDLE的安装位置还是在pycharm的安装位置，我导入virtualenv-win，安装文件里也没有看到这个包啊
   

老师，我的代码是按照老师视频里面一步一步来的，为啥我创建出来的项目名字就是我存放代码的文件夹的名字呢？

老师您好，int转为str，为什么报错，int可以转化为str吗？

老师，之前的网络配置和老师应该是一样的，现在防火墙也关了，就是进不去tomcat

处理中文出现问题,不是乱码,全是???问好

代码:

public class servletDemo01 extends HttpServlet {
    @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        PrintWriter pw = resp.getWriter();
        pw.println("<!DOCTYPE html>\n" +
                "<html lang=\"en\">\n" +
                "<head>\n" +
                "    <meta charset=\"UTF-8\">\n" +
                "    <title>响应测试</title>\n" +
                "</head>\n" +
                "<body>");
        pw.println("响应测试helloworld");
        pw.println("</body>\n" +
                "</html>");

        pw.flush();
        pw.close();

    }
}

运行效果: