JDBC 的 PreparedStatement 与 Statement

 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.Statement;
 import java.util.Date;

 public class StatmentExample {

     public static void main(String[] args) throws Exception {
         mysqlConnection3();
     }

     // mysql 获取自增id的值的方法
     public static void mysqlConnection1() throws Exception {
         Class.forName("com.mysql.jdbc.Driver");
         String url = "jdbc:mysql://localhost/test?useUnicode=true&&characterEncoding=UTF-8&autoReconnect=true";
         String user = "root";
         String password = "123456";
         Connection conn = null;
         Statement stmt = null;
         ResultSet rs = null;

         try {
             conn = DriverManager.getConnection(url, user, password);
             stmt = conn.createStatement();
             stmt.executeUpdate("insert into dept (deptname) values ('市场部')", Statement.RETURN_GENERATED_KEYS);
             rs = stmt.getGeneratedKeys();// mysql 获取自增id的值的方法
             if (rs.next()) {
                 System.out.println(rs.getInt(1));
             }
         } catch (Exception e) {
             throw e;
         } finally {
             rs.close();
             stmt.close();
             conn.close();
         }
     }
     // 建议始终以 PreparedStatement 代替 Statement
     // 1.虽然代码多出几行，但可读性和可维护性得到提升
     // 2.防止SQL注入提高安全性，占位符中的内容都会被转义，['w' or '1' = '1']会被转义成[\'\\'w\\' or \\'1\\' = \\'1\\'\']
     // 3.虽然预编译要耗费时间，但sql编译后的执行代码被缓存下来，下次调用时就不需要编译，从而提升性能
     public static void mysqlConnection2() throws Exception {
         Class.forName("com.mysql.jdbc.Driver");
         String url = "jdbc:mysql://localhost/test?useUnicode=true&&characterEncoding=UTF-8&autoReconnect=true";
         String user = "root";
         String password = "123456";
         Connection conn = null;
         PreparedStatement perstmt2 = null;
         ResultSet rs2 = null;

         try {
             conn = DriverManager.getConnection(url, user, password);
             String sql2 = "select deptno,deptname from dept where deptno = ? ";// dept这张表有deptno，deptname字段
             perstmt2 = conn.prepareStatement(sql2);
             perstmt2.setInt(1,11);
             rs2 = perstmt2.executeQuery();
             while (rs2.next()) {
                 System.out.print(rs2.getInt("deptno") + "    ");
                 System.out.println(rs2.getString("deptname"));
             }
         } catch (Exception e) {
             throw e;
         } finally {
             // 不要只关闭conn，因为数据库那边的资源确实释放了，但是java这边的操作系统中的连接资源不会即时释放
             rs2.close();
             perstmt2.close();
             conn.close();
         }
     }
     // 使用PreparedStatement的AddBatch()方法一次性发送多个sql给数据库
     public static void mysqlConnection3() throws Exception {
         Class.forName("com.mysql.jdbc.Driver");
         String url = "jdbc:mysql://localhost/test?useUnicode=true&&characterEncoding=UTF-8&autoReconnect=true";
         String user = "root";
         String password = "123456";
         Connection conn = null;
         PreparedStatement perstmt2 = null;

         try {
             conn = DriverManager.getConnection(url, user, password);
             System.out.println((new Date()).getTime());
             perstmt2 = conn.prepareStatement("insert into dept (deptname) values (?)");
             for (int n = 0; n < 1000; n++) {
                 perstmt2.setString(1, "信息部" + n);
                 perstmt2.addBatch();
             }
             perstmt2.executeBatch();
             System.out.println((new Date()).getTime());
         } catch (Exception e) {
             throw e;
         } finally {
             perstmt2.close();
             conn.close();
         }
     }
 }