[无名弟子]Thrudy|2017年07月31日的日报-技能树.IT修真院

发表于： 2017-07-31 16:32:59

2 963

今日完成：

抽彩游戏代码：

package com.jinhege;

import java.util.Arrays;
import java.util.Scanner;

public class LotteryDrawing {

    public static void main(String[] args) {
        // write your code here
        Scanner in = new Scanner(System.in);
        System.out.println("How many numbers do you need to draw?");//draw 抽彩/抽签/抽奖
        int k = in.nextInt();

        System.out.println("What is the highest number you can draw?");
        int n = in.nextInt();

        //fill an array with number 1 2 3 ...n
        int[] numbers = new int[n];
        for (int i = 0; i < numbers.length; i++)
            numbers[i] = i + 1;

        //draw k numbers and put them into a second array
        int[] result = new int[k];
        for (int i = 0; i < result.length; i++) {
            //make a random index between 0 and n-1
            int r = (int) (Math.random() * n);

            //pick the element at the random location
            result[i] = numbers[r];

            /*确保不会再次抽取到那个数值，因为所有抽彩的数值必须不同，
            因此，这里用数组中的最后一个数值改写numbers[r]，并将n减1
             */
            //move the last element into the random location
            numbers[r] = numbers[n - 1];
            n--;
        }
        //print the sorted array
        Arrays.sort(result);
        System.out.println("Bet the following combination.It' ll make you rich!");
        for (int r : result)
            System.out.print(r+"    ");
    }
}

Console:

How many numbers do you need to draw?

What is the highest number you can draw?

Bet the following combination.It' ll make you rich!

7 30 69 71 88 94

Process finished with exit code 0

正常运行

明日计划：学习junit

遇到的问题：

表结构：

项目目录：

JdbcCustomerDao

package com.jinhege.customer.dao.impl;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.sql.DataSource;

import com.jinhege.customer.D.CustomerDAO;
import com.jinhege.customer.model.Customer;

public class JdbcCustomerDao implements CustomerDAO {
    private DataSource dataSource;

    public void setDataSource(DataSource dataSource) {
        this.dataSource = dataSource;
    }

    public void insert(Customer customer) {
        String sql = "INSERT INTO CUSTOMER" + "(cust_id,name,age)VALUES(?,?,?)";
        Connection conn = null;
        try {
            conn = dataSource.getConnection();
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setInt(1, customer.getCustId());
            ps.setString(2, customer.getName());
            ps.setInt(3, customer.getAge());
           // ps.executeUpdate();
            ps.close();
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            if (conn != null) {
                try {
                    conn.close();
                } catch (SQLException e) {

                }
            }
        }
    }

    public Customer findByCustomerId(int custId) {
        String sql = "SELECT *FROM CUSTOMER WHERE CUST_ID = ?";
        Connection conn = null;
        try {
            conn = dataSource.getConnection();
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setInt(1, custId);
            Customer customer = null;
            ResultSet rs = ps.executeQuery();
            if (rs.next()) {
                customer = new Customer(
                        rs.getInt("CUST_ID"),
                        rs.getString("NAME"),
                        rs.getInt("Age")
                );
            }
            rs.close();
            ps.close();
            return customer;
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            if (conn != null) {
                try {
                    conn.close();
                } catch (SQLException e) {

                }
            }
        }
    }

}

package com.jinhege.common;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.jinhege.customer.D.CustomerDAO;
import com.jinhege.customer.model.Customer;

public class App {
   public static void main(String[] args) {
      @SuppressWarnings("resource")
      ApplicationContext context = 
             new ClassPathXmlApplicationContext("application.xml");
           
           CustomerDAO customerDAO = (CustomerDAO) context.getBean("customerDAO");
           Customer customer = new Customer(1, "Thrudy",22);
           customerDAO.insert(customer);
          
           Customer customer1 = customerDAO.findByCustomerId(1);
           System.out.println(customer1);

   }
   
}

Spring-Customer.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://www.springframework.org/schema/beans
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

   <bean id="customerDAO"
   class="com.jinhege.customer.dao.impl.JdbcCustomerDao">
      <property name="dataSource" ref="dataSource" />
   </bean>
   </beans>

Spring-Datasource.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://www.springframework.org/schema/beans
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

   <bean id="dataSource"
      class="org.springframework.jdbc.datasource.DriverManagerDataSource">

      <property name="driverClassName" value="com.mysql.jdbc.Driver" />
      <property name="url" value="jdbc:mysql://localhost:3306/test?useSSL=false" />
      <property name="username" value="root" />
      <property name="password" value="jinhege" />
   </bean>

</beans>

application,xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://www.springframework.org/schema/beans
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

   <import resource="database/Spring-Datasource.xml" />
   <import resource="customer/Spring-Customer.xml" />

</beans>

注释下面这句后：

// ps.executeUpdate();

Console:

输出好怪异。。。

package com.jinhege.customer.model;

import java.sql.Timestamp;
//添加客户类型用来存储用户的数据
public class Customer {
   int custId;
   String name;
   int age;

   public Customer(int custId, String name, int age) {
   }

   public int getCustId() {
      return custId;
   }

   public String getName() {
      return name;
   }

public int getAge() {
      return age;
      }
      }

不注释：

ps.executeUpdate();

七月 31, 2017 2:47:38 下午 org.springframework.context.support.ClassPathXmlApplicationContext prepareRefresh

信息: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@2e0fa5d3: startup date [Mon Jul 31 14:47:38 CST 2017]; root of context hierarchy

七月 31, 2017 2:47:38 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

信息: Loading XML bean definitions from class path resource [application.xml]

七月 31, 2017 2:47:39 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

信息: Loading XML bean definitions from class path resource [database/Spring-Datasource.xml]

七月 31, 2017 2:47:39 下午 org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

信息: Loading XML bean definitions from class path resource [customer/Spring-Customer.xml]

七月 31, 2017 2:47:39 下午 org.springframework.jdbc.datasource.DriverManagerDataSource setDriverClassName

信息: Loaded JDBC driver: com.mysql.jdbc.Driver

Exception in thread "main" java.lang.RuntimeException: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column 'NAME' cannot be null

at com.jinhege.customer.dao.impl.JdbcCustomerDao.insert(JdbcCustomerDao.java:31)

at com.jinhege.common.App.main(App.java:16)

Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column 'NAME' cannot be null

at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)

at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)

at java.lang.reflect.Constructor.newInstance(Constructor.java:423)

at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)

at com.mysql.jdbc.Util.getInstance(Util.java:408)

at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:935)

at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3973)

at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3909)

at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2527)

at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2680)

at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2490)

at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1858)

at com.mysql.jdbc.PreparedStatement.executeUpdateInternal(PreparedStatement.java:2079)

at com.mysql.jdbc.PreparedStatement.executeUpdateInternal(PreparedStatement.java:2013)

at com.mysql.jdbc.PreparedStatement.executeLargeUpdate(PreparedStatement.java:5104)

at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1998)

at com.jinhege.customer.dao.impl.JdbcCustomerDao.insert(JdbcCustomerDao.java:28)

... 1 more

Process finished with exit code 1

'NAME' cannot be null

思考过可能程序中插入数据失败，在dos里插入了数据：

但是运行结果还是一样。。。

嗯，这个问题又卡了三天，一直解决不了。。。嗯，学junit，来定位问题，这样看错误调又调不对太浪费时间了。

收获：

数组排序：

对数值型数组进行排序，可以使用Arrays类中的sort方法：

Math.random()方法返回一个0到1之间（包含0不包含1）的随机浮点数。

int r = (int)(Math.random()*n); //[0,n-1] 双闭

方法executeUpdate()

用于执行INSERT,UPDATE或DELETE语句以及SQL DDL(数据定义语言)语句如create table 和 drop table

insert,update或delete语句的效果是修改表中0行或多行中的一列或多列

executeUpdate的返回值是一个整数，指示受影响的行数（即更新计数）

对于create table 和 drop table等不操作行的语句，excuteUpdate的返回值总为0

代码块”有两种流行（也是行业都遵守的习惯）的写法，

即Allmans风格和Kernighan风格
Allmans风格：
Allmans风格也称“独行”风格，即左、右大括号各自独占一行

当代码量较少时适合使用“独行”风格，此时代码布局清晰、可读性强。

Kernighan风格：
Kernighan风格也称“行尾”风格，即左大括号在上一行的行尾，而右大括号独占一行

当代码量较多时不适合使用“独行”风格，因为该风格将导致代码的左半部分出现大量的左、右大括号，导致代码清晰度下降，这时应当使用“行尾”风格。

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【任务1】 [无名弟子]Thrudy | 2017年07月31日 的日报 中品

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【任务1】 [无名弟子]Thrudy | 2017年07月31日的日报中品