PreparedStatement接口详解

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PerparedStatement接口详解：
一、jdbc工具类扩展：

//close()方法重载    public static void close(Connection conn,Statement stmt,ResultSet rs){        if(rs!=null){            try {                rs.close();            } catch (SQLException e) {                e.printStackTrace();                throw new RuntimeException(e);            }        }        if(stmt!=null){            try {                stmt.close();            } catch (SQLException e) {                e.printStackTrace();                throw new RuntimeException(e);            }        }        if(conn!=null){            try {                conn.close();            } catch (SQLException e) {                e.printStackTrace();                throw new RuntimeException(e);            }        }    }

二、PreparedStatement执行增删改的sql语句：

package sram.jdbc.connection;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.SQLException;import org.junit.Test;import sram.util.jdbc.JdbcUtil;/** * PreparedStatement执行sql语句 */public class Demo4 {    /**     * 插入、修改、删除     */    @Test    public void test(){        Connection conn = null;        PreparedStatement stmt = null;        try {            //1.获取连接            conn = JdbcUtil.getConnection();            //2.准备预编译的sql            //插入：String sql = "INSERT INTO dept(NAME,BossName) VALUES(?,?)";//?表示一个参数的占位符            //修改：String sql = "UPDATE dept SET BossName=? WHERE id=?";            //删除：            String sql = "DELETE FROM dept WHERE id=?";            //3.执行预编译sql语句(检查语法)            stmt = conn.prepareStatement(sql);            //4.设置参数值            /**             * 参数一： 参数位置  从1开始             */            /*插入：            stmt.setString(1, "财务部");            stmt.setString(2, "孙五");            */            /*修改            stmt.setString(1, "钱八");            stmt.setInt(2, 7);            */            //删除：            stmt.setInt(1, 7);            //5.发送参数，执行sql。不同于Statement接口的该方法，这里()不带sql语句。            int count = stmt.executeUpdate();            System.out.println("影响了"+count+"行");        } catch (SQLException e) {            e.printStackTrace();            throw new RuntimeException(e);        }finally{            JdbcUtil.close(conn, stmt);        }    }}

三、PreparedStatement执行查询的sql语句：

package sram.jdbc.connection;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import org.junit.Test;import sram.util.jdbc.JdbcUtil;/** * 查询 */public class Demo5 {    @Test    public void test(){        Connection conn = null;        PreparedStatement stmt = null;        ResultSet rs = null;        try {            //1.获取连接            conn = JdbcUtil.getConnection();            //2.准备预编译的sql            String sql = "SELECT * FROM dept";            //3.预编译            stmt = conn.prepareStatement(sql);            //4.执行sql            rs = stmt.executeQuery();            //5.遍历rs            while(rs.next()){                int id =rs.getInt("id");                String name =rs.getString("NAME");                String bossName = rs.getString("BossName");                System.out.println(id+","+name+","+bossName);            }        } catch (SQLException e) {            e.printStackTrace();            throw new RuntimeException(e);        }finally{            //关闭资源            JdbcUtil.close(conn, stmt, rs);        }    }}

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