JDBC实现数据库增删改查功能

jdbc，简单点来说，就是用java操作数据库，下面简单介绍怎么实现数据库的增删改查功能。

1、添加数据

package cn.itcast.jdbc;

import java.sql.*;

public class jdbcdemo2 {

    public static void main(string[] args) {

        connection connection = null;
        preparedstatement preparedstatement = null;

        try {
            //1、注册驱动
            class.forname("com.mysql.jdbc.driver");
            //2、定义sql
            string sql = "insert into course values(?,?,?)";
            //3、获取connection对象
            //student表示你要操作的数据库
            //如果是locakhost：3306，也可以简写为"jdbc:mysql:///student"
            connection = drivermanager.getconnection("jdbc:mysql://localhost:3306/student","root","root");
            //4、获取执行sql的对象
            preparedstatement = connection.preparestatement(sql);
            //传入参数
            preparedstatement.setint(1,5);
            preparedstatement.setstring(2,"javaweb");
            preparedstatement.setint(3,88);
            //5、执行sql
            int count = preparedstatement.executeupdate();
            //6、处理结果
            system.out.println(count);
            if (count > 0) {
                system.out.println("添加成功");
            } else {
                system.out.println("添加失败");
            }
        } catch (classnotfoundexception e) {
            e.printstacktrace();
        } catch (sqlexception e) {
            e.printstacktrace();
        } finally {
            //7、释放资源
            //避免空指针异常
            if (preparedstatement != null) {
                try {
                    preparedstatement.close();
                } catch (sqlexception e) {
                    e.printstacktrace();
                }
            }
            if (connection != null) {
                try {
                    connection.close();
                } catch (sqlexception e) {
                    e.printstacktrace();
                }
            }
        }
    }
}

2、删除数据

package cn.itcast.jdbc;

import java.sql.*;

public class jdbcdemo4 {
    public static void main(string[] args) {
        connection connection = null;
        preparedstatement preparedstatement = null;
        try {
            //1、注册驱动
            class.forname("com.mysql.jdbc.driver");

            //2、获取连接对象
            connection = drivermanager.getconnection("jdbc:mysql://localhost:3306/student","root","root");

            //3、定义sql
            string sql = "delete from course where cno = ?";

            //4、获取执行sql对象
            preparedstatement = connection.preparestatement(sql);
            preparedstatement.setint(1,5);

            //5、执行sql
            int count = preparedstatement.executeupdate();

            //6、处理结果
            system.out.println(count);
            if (count > 0) {
                system.out.println("删除成功");
            } else {
                system.out.println("删除失败");
            }

        } catch (classnotfoundexception e) {
            e.printstacktrace();
        } catch (sqlexception e) {
            e.printstacktrace();
        } finally {
            //7、释放资源
            if (preparedstatement != null) {
                try {
                    preparedstatement.close();
                } catch (sqlexception e) {
                    e.printstacktrace();
                }
            }
            if (connection != null) {
                try {
                    connection.close();
                } catch (sqlexception e) {
                    e.printstacktrace();
                }
            }
        }

    }
}

3、修改数据

package cn.itcast.jdbc;

import java.sql.*;

public class jdbcdemo3 {
    public static void main(string[] args) {
        connection connection = null;
        preparedstatement preparedstatement = null;
        try {
            //1、注册驱动
            class.forname("com.mysql.jdbc.driver");

            //2、获取连接对象
            connection = drivermanager.getconnection("jdbc:mysql://localhost:3306/student", "root", "root");

            //3、定义sql
            string sql = "update course set period = ? where cno = ?";

            //4、获取执行sql对象
            preparedstatement = connection.preparestatement(sql);
            //设置参数
            preparedstatement.setint(1,90);
            preparedstatement.setint(2,1);


            //5、执行sql
            int count = preparedstatement.executeupdate();

            //6、处理结果
            system.out.println(count);
            if (count > 0) {
                system.out.println("修改成功！");
            } else {
                system.out.println("修改失败！");
            }
        } catch (classnotfoundexception e) {
            e.printstacktrace();
        } catch (sqlexception e) {
            e.printstacktrace();
        } finally {
            //7、释放资源
            if (preparedstatement != null) {
                try {
                    preparedstatement.close();
                } catch (sqlexception e) {
                    e.printstacktrace();
                }
            }
            if (connection != null) {
                try {
                    connection.close();
                } catch (sqlexception e) {
                    e.printstacktrace();
                }
            }
        }

    }
}

4、查询数据

package cn.itcast.jdbc;

import cn.itcast.domain.course;

import java.sql.*;
import java.util.arraylist;
import java.util.list;

public class jdbcdemo5 {

    /**
     * 查询所有course对象
     * @return
     */
    public static void main(string[] args) {
        connection connection = null;
        preparedstatement preparedstatement = null;
        resultset resultset = null;
        list<course> list = null;
        try {
            //1、注册驱动
            class.forname("com.mysql.jdbc.driver");
            //2、获取连接
            connection = drivermanager.getconnection("jdbc:mysql://localhost:3306/student", "root", "root");

            //3、定义sql
            string sql = "select * from course";
            //4、获取执行sql的对象
            preparedstatement = connection.preparestatement(sql);
            //5、执行sql
            resultset = preparedstatement.executequery();
            //6、遍历结果集，封装对象，装载集合
            course course = null;
            list = new arraylist<course>();
            while (resultset.next()) {
                //获取数据
                int cno = resultset.getint("cno");
                string cname = resultset.getstring("cname");
                int period = resultset.getint("period");
                //创建course对象并赋值
                course = new course();
                course.setcno(cno);
                course.setcname(cname);
                course.setperiod(period);
                //装载集合
                list.add(course);

            }
        } catch (classnotfoundexception e) {
            e.printstacktrace();
        } catch (sqlexception e) {
            e.printstacktrace();
        } finally {
            if (resultset != null) {
                try {
                    resultset.close();
                } catch (sqlexception e) {
                    e.printstacktrace();
                }
            }
            if (preparedstatement != null) {
                try {
                    preparedstatement.close();
                } catch (sqlexception e) {
                    e.printstacktrace();
                }
            }
            if (connection != null) {
                try {
                    connection.close();
                } catch (sqlexception e) {
                    e.printstacktrace();
                }
            }
        }
        system.out.println(list);
    }

}

我们可以发现，增删改的操作基本都是差不多的语句，且执行sql的语句都是一样的，都是preparedstatement.executeupdate()。但查询操作就有所不同了，返回的是一个结果集，且执行sql的语句就是preparedstatement.executequery()。

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