后端开发PreparedStatement的优点以及实现高效批量插入

Posted 2023-02-27 cls1277

知识点基本都在代码的注释里

PreparedStatement比Statement好在：
1.可以操作数据库中blob的数据
2.可以高效批量插入
3.防止SQL注入，可以预编译

这部分有一些小细节，已经在代码中写出来了

package com.cls1277.insertblob;

import com.cls1277.preparedstatement.StatementTest;
import com.cls1277.preparedstatement.customer.Customer;
import com.cls1277.utils.JDBCutils;
import org.junit.Test;

import javax.xml.ws.RequestWrapper;
import java.io.*;
import java.sql.*;
import java.text.SimpleDateFormat;
import java.util.Properties;

public class BlobInsert 
    @Test
    public void testInsert()  
        Connection conn = null;
        PreparedStatement ps = null;
        try 
            conn = JDBCutils.getConnection();
            String sql = "insert into customers(name, email, birth, photo)values(?,?,?,?)";
            ps = conn.prepareStatement(sql);
            ps.setObject(1, "曹老师");
            ps.setObject(2, "[e-mail]");
            ps.setObject(3, "2002-06-10");
            //添加Blob
            FileInputStream fis = new FileInputStream(new File("E:/cls1277/Free/image.jpg"));
            ps.setBlob(4, fis);
            ps.execute();
         catch (Exception e) 
            e.printStackTrace();
         finally 
            JDBCutils.closeResource(conn, ps);
        
    

    @Test
    public void testQueryBlob() 
        Connection conn = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        InputStream is = null;
        FileOutputStream fos = null;
        try 
            conn = JDBCutils.getConnection();
//            String sql = "insert into customers(name, email, birth, photo)values(?,?,?,?)";
            String sql = "select id,name,email,birth,photo from customers where id = ?";
            ps = conn.prepareStatement(sql);
            ps.setObject(1, 21);
            rs = ps.executeQuery();
            if(rs.next()) 
                //方式1
                int id = rs.getInt(1);
                String name = rs.getString(2);
                String email = rs.getString(3);
                Date birth = rs.getDate(4);
                //方式2：更好一点
//                int id1 = rs.getInt("id");
//                String name1 = rs.getString("name");
//                String email1 = rs.getString("email");
//                Date birth1 = rs.getDate("birth");
                Customer customer = new Customer(id, name, email, birth);
                System.out.println(customer);
                //将photo保存到本地
                Blob photo = rs.getBlob("photo");
                //文件的保存
                //当图片过大时虽然满足Blob类型的大小，但是得修改max_allow_packet的大小，mysql 8.0已经默认4M。
                is = photo.getBinaryStream();
                fos = new FileOutputStream(new File("save.jpg"));
                byte[] buffer = new byte[1024];
                int len;
                while((len = is.read(buffer)) != -1) 
                    fos.write(buffer, 0, len);
                
            
         catch (Exception e) 
            e.printStackTrace();
         finally 
            JDBCutils.closeResource(conn, ps, rs);
            try 
                if(is!=null)
                    is.close();
             catch (IOException e) 
                e.printStackTrace();
            
            try 
                if(fos!=null)
                    fos.close();
             catch (IOException e) 
                e.printStackTrace();
            
        
    

    //使用PreparedStatement实现批量操作：预编译
    @Test
    public void testMultiInsert() 
        Connection conn = null;
        PreparedStatement ps = null;
        try 
            conn = JDBCutils.getConnection();
            String sql = "insert into customers(name) values(?)";
            ps = conn.prepareStatement(sql);
            for(int i=0; i<20000; i++) 
                ps.setObject(1, "name_"+i);
                ps.execute();
            
         catch (Exception e) 
            e.printStackTrace();
         finally 
            JDBCutils.closeResource(conn, ps);
        
    

    //PreparedStatement批量插入优化
    @Test
    public void testMultiInsert2() 
        Connection conn = null;
        PreparedStatement ps = null;
        try 
            conn = JDBCutils.getConnection();
            String sql = "insert into customers(name) values(?)";
            ps = conn.prepareStatement(sql);
            for(int i=0; i<20000; i++) 
                ps.setObject(1, "name_"+i);
                //1.攒
                ps.addBatch();
                if(i%500==0) 
                    //2.攒够了 执行一次
                    ps.executeBatch();
                    //3.执行了 清空一次
                    ps.clearBatch();
                    //4.注意判断不整除的情况
                    //如果不能运行Batch，则在配置文件的url后面加上：?rewriteBatchedStatement=true
                    //如果不能批量操作，则换新的驱动
                
            
         catch (Exception e) 
            e.printStackTrace();
         finally 
            JDBCutils.closeResource(conn, ps);
        
    

    //PreparedStatement批量插入进一步优化：最高效
    @Test
    public void testMultiInsert3() 
        Connection conn = null;
        PreparedStatement ps = null;
        try 
            conn = JDBCutils.getConnection();
            //优化：不允许自动提交（不着急提交）
            conn.setAutoCommit(false);
            String sql = "insert into customers(name) values(?)";
            ps = conn.prepareStatement(sql);
            for(int i=0; i<20000; i++) 
                ps.setObject(1, "name_"+i);
                //1.攒
                ps.addBatch();
                if(i%500==0) 
                    ps.executeBatch();
                    ps.clearBatch();
                
                //最后一起提交
                conn.commit();
            
         catch (Exception e) 
            e.printStackTrace();
         finally 
            JDBCutils.closeResource(conn, ps);