JDBC概述

发表于 更新于 分类于 阅读次数： Valine：

JDBC复习回顾

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import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.sql.*;
import java.util.Properties;

/**
 * @author zss
 */
public class GetInfor {
    public static void main(String[] args) throws ClassNotFoundException, IOException, SQLException {
        Properties properties=new Properties();
        properties.load(new FileReader("src\\Information.properties"));
        String jdbc= properties.getProperty("jdbcJar");
        String url= properties.getProperty("url");
        String password= properties.getProperty("password");
        String user= properties.getProperty("user");
        Class.forName(jdbc);
        Connection connection= DriverManager.getConnection(url,user,password);
        String selectSql="select * from user where name= ? ";
        PreparedStatement preparedStatement= connection.prepareStatement(selectSql);
        preparedStatement.setString(1,"郭富城");
        ResultSet resultSet= preparedStatement.executeQuery();
        if (resultSet.next()){
            System.out.println(resultSet.getString("name"));
        }
    }
}

image-20220329235249837

练习

添加custom

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import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.Properties;
import java.util.Scanner;

/**
 * @author zss
 */
public class CustomerAdd {
    public static void main(String[] args) throws SQLException, IOException, ClassNotFoundException {
        CustomerAdd customerAdd=new CustomerAdd();
        customerAdd.addPerson();
    }
    public void addPerson() throws SQLException, IOException, ClassNotFoundException {
        Scanner scanner=new Scanner(System.in);
        System.out.println("请输入添加的用户名");
        String name=scanner.next();
        System.out.println("请输入添加邮箱");
        String email=scanner.next();
        System.out.println("请输入添加的生日");
        String birthday=scanner.next();
        String mysqlInsert= "insert into customers (name,email,birth) values(?,?,?)";
        dateAdd(mysqlInsert,name,email,birthday);

    }
    public void dateAdd(String sql,Object ...obj) throws IOException, ClassNotFoundException, SQLException {
        Properties properties=new Properties();
        properties.load(new FileReader("src\\Information.properties"));
        String jdbc= properties.getProperty("jdbcJar");
        String url= properties.getProperty("url");
        String password= properties.getProperty("password");
        String user= properties.getProperty("user");
        Class.forName(jdbc);
        Connection connection= DriverManager.getConnection(url,user,password);
        PreparedStatement preparedStatement= connection.prepareStatement(sql);
        for (int i=0;i<obj.length;i++){
            preparedStatement.setObject(i+1,obj[i]);
        }
        int count=preparedStatement.executeUpdate();
        if (count==1){
            System.out.println("插入成功");
        }else {
            System.out.println("插入失败");
        }

        preparedStatement.close();
        connection.close();

    }

}

存储数据库的图片与视频

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preparedStatement.setBlob(4,new BufferedInputStream(new FileInputStream(new File("D:\\壁纸\\女孩子.png"))));

注意，有时候我们使用了mediumBlog，但是还是插入不进去，这是因为mysql安装目录下，my.ini文件缺少相关发配置，加上max_allowed_packet=16M

批量插入

批量插入 中使用statement必须每一次都重新编译sql语句，但是preparementStament仅仅编译一次，其余使用占位符即可，使用for循环进行插入即可，只不过每一次的占位符不同

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Connection connection= DriverManager.getConnection(url,user,password);
PreparedStatement preparedStatement= connection.prepareStatement("insert into goods (name) VALUES (?)");
for (int i=0;i<200;i++){
preparedStatement.setObject(1,"goods"+i);
int count=preparedStatement.executeUpdate();
}

优化

addBatch：积攒sql语句

excuteBatch:执行sql语句

clearBatch：清空sql语句

默认情况下，mysql关闭批处理，所以我们需要一个参数开启

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url=jdbc:mysql://localhost:3306/test?rewriteBatchedStatements=true
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for (int i=500;i<=1000;i++){
    preparedStatement.setString(1,"goods"+i);
    preparedStatement.addBatch();
    if (i%500==0){
        preparedStatement.executeBatch();
        preparedStatement.clearBatch();
    }
}

这样会优化我们插入的效率

优化2

关闭自动提交

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Connection connection= DriverManager.getConnection(url,user,password);
connection.setAutoCommit(false);
PreparedStatement preparedStatement= connection.prepareStatement("insert into goods (name) VALUES (?)");
for (int i=500;i<=1000;i++){
    preparedStatement.setString(1,"goods"+i);
    preparedStatement.addBatch();
    if (i%500==0){
        preparedStatement.executeBatch();
        preparedStatement.clearBatch();
    }
}
connection.commit();