JAVA连接数据库（小白式）

本文中将列举三种不同的连接写法，但是本质上都为一种。

一、准备工作

1.1 找到JAR包

地址为数据库的安装路径，我的在E盘，以下为我的路径仅供参考。

1.2 给项目添加jar包

右击项目->properites->在列表中找到 Java Build Path->点击Libraties-> Add External JARs..->

二、开始操作

1、在一个文件中实现

test_jdbc.java

package test_wms; import java.sql.Connection; import java.sql.Date; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; public class test_jdbc { //oracle的驱动 static final String JDBC_DRIVER = "oracle.jdbc.driver.OracleDriver"; //连接数据库的路径 如果是本机@localhost static final String url = "jdbc:oracle:thin:@172.17.1.189:1522:mests"; static final String user = "root"; static final String password = "123456"; public static void main(String[] args) { Connection conn = null; Statement stmt = null; try { //建立驱动 Class.forName(JDBC_DRIVER); System.out.println("打开数据库中.."); //进行连接 conn = DriverManager.getConnection(url, user, password); System.out.println("实例化statement.."); stmt = conn.createStatement(); String sql; //编写sql sql = "select goods_barcode,goods_sku,create_date from test_goods_info"; ResultSet rs = stmt.executeQuery(sql); while (rs.next()) { String bar = rs.getString("goods_barcode"); String sku = rs.getString("goods_sku"); Date credate = rs.getDate("create_date"); System.out.println("条码:" + bar + "," + "sku:" + sku + "," + "创建时间：" + credate); } rs.close(); stmt.close(); conn.close(); } catch (SQLException se) { se.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } finally { // 再次关闭 try { if (stmt != null) stmt.close(); } catch (SQLException se2) { } try { if (conn != null) conn.close(); } catch (SQLException se) { se.printStackTrace(); } } System.out.println("執行結束!"); } }

2、第二个为进阶版，把连接抛给Conn的文件处理。

Conn.java

package test_wms; import java.io.FileInputStream; import java.io.InputStream; import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.util.Properties; public class Conn { static final String driverClass = "oracle.jdbc.driver.OracleDriver"; static final String url="jdbc:oracle:thin:@172.17.1.189:1522:mests"; static final String username="root"; static final String password="123456"; public static Connection getconn() { Connection conn=null; try { Class.forName(driverClass); conn=DriverManager.getConnection(url,username,password); System.out.println("連接成功！"); } catch (SQLException se) { System.out.println("conn的數據庫配置有問題"); se.printStackTrace(); }catch (Exception e) { e.printStackTrace(); } return conn; } }

test_select.java

package test_wms; import java.sql.Connection; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; public class test_select { public static void main(String[] args) { Connection conn=null; Statement st=null; ResultSet rs=null; try { conn=Conn.getconn(); st=conn.createStatement(); String sql; sql="select goods_barcode,goods_sku from test_goods_info"; rs=st.executeQuery(sql); while(rs.next()) { String bar=rs.getString("goods_barcode"); String sku=rs.getString("goods_sku"); System.out.println("條碼:"+bar+","+"SKU:"+sku); } rs.close(); st.close(); conn.close(); } catch (SQLException se) { System.out.println("獲取的數據庫配置有問題"); se.printStackTrace(); }catch (Exception e) { e.printStackTrace(); }finally { // 再次關閉 try { if (st != null) st.close(); } catch (SQLException se2) { } try { if (conn != null) conn.close(); } catch (SQLException se) { se.printStackTrace(); } } }}

3、这是作为真正项目中会用到的方式->将配置存入.properites文件中

3.1 创建一个config文件放入database.properties

**注意：

文件存放的路径关系到DbUtil.java->FileInputStream("config/database.properties");这里的路径。如果错误会报错系统找不到该文件。database.properties中的键值对一定要和DbUtil.java中获取的一样，否者空指针异常。

 

database.properties

database=ORACLE driverClass = oracle.jdbc.driver.OracleDriver timeout = 10 url = jdbc:oracle:thin:@172.17.1.189:1522:mests username = mesap password = mesap

DbUtil.java

package test_wms; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.io.InputStream; import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.util.Properties; public class DbUtil { static String driverClass = null; static String url = null; static String username = null; static String password = null; static { //创建properties对象，获取配置信息 //路径记得配置 try { Properties properties=new Properties(); InputStream input=new FileInputStream("config/database.properties"); properties.load(input); driverClass=properties.getProperty("driverClass"); url=properties.getProperty("url"); username=properties.getProperty("username"); password=properties.getProperty("password"); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public static Connection getconn() { Connection conn=null; try { Class.forName(driverClass); conn=DriverManager.getConnection(url,username,password); System.out.println("連接成功！"); } catch (SQLException se) { System.out.println("conn的數據庫配置有問題"); se.printStackTrace(); }catch (Exception e) { e.printStackTrace(); } return conn; } }

test_select.java

package test_wms; import java.sql.Connection; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; public class test_select { public static void main(String[] args) { Connection conn=null; Statement st=null; ResultSet rs=null; try { conn=DbUtil.getconn(); st=conn.createStatement(); String sql; sql="select goods_barcode,goods_sku from test_goods_info"; rs=st.executeQuery(sql); while(rs.next()) { String bar=rs.getString("goods_barcode"); String sku=rs.getString("goods_sku"); System.out.println("條碼:"+bar+","+"SKU:"+sku); } rs.close(); st.close(); conn.close(); } catch (SQLException se) { System.out.println("獲取的數據庫配置有問題"); se.printStackTrace(); }catch (Exception e) { e.printStackTrace(); }finally { // 再次關閉 try { if (st != null) st.close(); } catch (SQLException se2) { } try { if (conn != null) conn.close(); } catch (SQLException se) { se.printStackTrace(); } } }}

以上，完结撒花✿✿ヽ(°▽°)ノ✿