JBDC入门

• 导包：
  
• 数据库

CREATE DATABASE mydb;
#使用数据库
USE mydb;
###创建分类表
CREATE TABLE category(
  cid INT PRIMARY KEY AUTO_INCREMENT  ,
  cname VARCHAR(100)
);
#初始化数据
INSERT INTO category (cname) VALUES('家电');
INSERT INTO category (cname) VALUES('服饰');
INSERT INTO category (cname) VALUES('化妆品');

• 获取数据库数据

package bull01.JBDCBasis;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

import org.junit.Test;

public class JDBCDemo_01 {
    @Test
    public void method1() throws Exception {
        //1.注册驱动
        Class.forName("com.mysql.jdbc.Driver");
        //2.获得连接,三个参数url,user,password
        Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "root", "root");
        //3.获得语句执行者
        Statement st = conn.createStatement();
        //4.执行SQL语句
        ResultSet rs = st.executeQuery("select * from category");
        //5.处理结果集
        /*
         * rs.next()指向下一行。true:有效；false:尾。
         * rs.previous()指向上一行。true:有效；false:头。
         */
        while(rs.next()) {
            Integer cid = rs.getInt("cid");
            String cname = rs.getString("cname");
            System.out.println(cid+"---"+cname);
        }
        //6.释放资源
        /*
         * 后开先关
         * 从下往上关
         */
        rs.close();
        st.close();
        conn.close();
    }
}

• 不抛去异常，采用try···catch方式

package bull01.JBDCBasis;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import org.junit.Test;

public class JDBCDemo_02 {
    @Test
    public void method1()  {
        //1.注册驱动
        //2.获得连接,三个参数url,user,password
        Connection conn = null;
        //3.获得语句执行者
        Statement st = null;
        //4.执行SQL语句
        ResultSet rs = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb", "root", "root");
            st = conn.createStatement();
            rs = st.executeQuery("select * from category");
            //5.处理结果集
            /*
             * rs.next()指向下一行。true:有效；false:尾。
             * rs.previous()指向上一行。true:有效；false:头。
             */
            while(rs.next()) {
                Integer cid = rs.getInt("cid");
                String cname = rs.getString("cname");
                System.out.println(cid+"---"+cname);
            }
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        //6.释放资源
        /*
         * 后开先关
         * 从下往上关
         */
        if(rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

        if(st != null) {
            try {
                st.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

        if(conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
}