在src下创建jdbc.properties文件
jdbc.properties内容如下:
driverClass=com.mysql.jdbc.Driver
url = jdbc:mysql://localhost/jdbc
name = root
password = root
改动的JDBCUtil:
JDBCTest:
package com.test.example;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import com.mysql.jdbc.Driver;
import com.test.util.JDBCUtil;
public class JDBCTest {
public static void main(String[] args) {
// TODO Auto-generated method stub
Connection connection = null;
Statement statement = null;
ResultSet resultSet = null;
try {
//1. 注册驱动
connection = JDBCUtil.getConn();
/*
//Driver 这个类里面有静态代码块,一上来就执行了,所以等同于我们注册了两次驱动。 其实没这个必要的。
//静态代码块 ---> 类加载了,就执行。 java.sql.DriverManager.registerDriver(new Driver());
//DriverManager.registerDriver(new com.mysql.jdbc.Driver());
Class.forName("com.mysql.jdbc.Driver");
//2. 建立连接 参数一: 协议 + 访问的数据库 , 参数二: 用户名 , 参数三: 密码。
connection = DriverManager.getConnection("jdbc:mysql://localhost/jdbc", "root", "root");*/
//3. 创建statement , 跟数据库打交道,一定需要这个对象
statement = connection.createStatement();
//4. 执行查询 , 得到结果集
String sql = "select * from stu";
resultSet = statement.executeQuery(sql);
//5. 遍历查询每一条记录
while(resultSet.next()){
int id = resultSet.getInt("id");
String name = resultSet.getString("name");
int age = resultSet.getInt("age");
System.out.println("id="+id+",name="+name+",age="+age);
}
// resultSet.close();
// Statement.close();
// connection.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
JDBCUtil.close(connection, resultSet, statement);
}
}
}
JDBCUtil[错误示例]:
package com.test.util;
import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
public class JDBCUtil {
static String driverClass = null;
static String url = null;
static String name = null;
static String password = null;
//读取jdbc.properties
static{
try {
//1.创建一个属性配置对象
Properties properties = new Properties();
//对应文件位于工程根目录
InputStream is = new FileInputStream("jdbc.properties");
//2.导入输入流,抓取异常
properties.load(is);
//3.读取属性
driverClass = properties.getProperty("driverClass");
url = properties.getProperty("url");
name = properties.getProperty("name");
password = properties.getProperty("password");
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
}
/**
* 注册驱动 建立参数
* <p>Title: close</p>
* <p>Description: </p>
* @param connection
* @param resultSet
* @param statement
*/
public static Connection getConn(){
Connection connection = null;
//2. 建立连接 参数一: 协议 + 访问的数据库 , 参数二: 用户名 , 参数三: 密码。
try {
Class.forName(driverClass);
connection = DriverManager.getConnection(url, name, password);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return connection;
}
/**
* 释放资源
* <p>Title: close</p>
* <p>Description: </p>
* @param connection
* @param resultSet
* @param statement
*/
public static void close(Connection connection,ResultSet resultSet,Statement statement){
closeRS(resultSet);
closeSt(statement);
closeConn(connection);
}
private static void closeRS(ResultSet resultSet){
try {
if(resultSet !=null){
resultSet.close();
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
resultSet = null;
}
}
private static void closeSt(Statement statement){
try {
if(statement !=null){
statement.close();
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
statement = null;
}
}
private static void closeConn(Connection connection){
try {
if(connection !=null){
connection.close();
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
connection = null;
}
}
}
数据库:
运行结果:
正确示例1:
jdbc.properties在工程的根目录下:
JDBCTest:
package com.test.example;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import com.mysql.jdbc.Driver;
import com.test.util.JDBCUtil;
public class JDBCTest {
public static void main(String[] args) {
// TODO Auto-generated method stub
Connection connection = null;
Statement statement = null;
ResultSet resultSet = null;
try {
//1. 注册驱动
connection = JDBCUtil.getConn();
/*
//Driver 这个类里面有静态代码块,一上来就执行了,所以等同于我们注册了两次驱动。 其实没这个必要的。
//静态代码块 ---> 类加载了,就执行。 java.sql.DriverManager.registerDriver(new Driver());
//DriverManager.registerDriver(new com.mysql.jdbc.Driver());
Class.forName("com.mysql.jdbc.Driver");
//2. 建立连接 参数一: 协议 + 访问的数据库 , 参数二: 用户名 , 参数三: 密码。
connection = DriverManager.getConnection("jdbc:mysql://localhost/jdbc", "root", "root");*/
//3. 创建statement , 跟数据库打交道,一定需要这个对象
statement = connection.createStatement();
//4. 执行查询 , 得到结果集
String sql = "select * from stu";
resultSet = statement.executeQuery(sql);
//5. 遍历查询每一条记录
while(resultSet.next()){
int id = resultSet.getInt("id");
String name = resultSet.getString("name");
int age = resultSet.getInt("age");
System.out.println("id="+id+",name="+name+",age="+age);
}
// resultSet.close();
// Statement.close();
// connection.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
JDBCUtil.close(connection, resultSet, statement);
}
}
}
jdbc.properties:
driverClass=com.mysql.jdbc.Driver
url = jdbc:mysql://localhost/jdbc
name = root
password = root
JDBCUtil:
package com.test.util;
import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
public class JDBCUtil {
static String driverClass = null;
static String url = null;
static String name = null;
static String password = null;
//读取jdbc.properties
static{
try {
//1.创建一个属性配置对象
Properties properties = new Properties();
//对应文件位于工程根目录
InputStream is = new FileInputStream("jdbc.properties");
//2.导入输入流,抓取异常
properties.load(is);
//3.读取属性
driverClass = properties.getProperty("driverClass");
url = properties.getProperty("url");
name = properties.getProperty("name");
password = properties.getProperty("password");
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
}
/**
* 注册驱动 建立参数
* <p>Title: close</p>
* <p>Description: </p>
* @param connection
* @param resultSet
* @param statement
*/
public static Connection getConn(){
Connection connection = null;
//2. 建立连接 参数一: 协议 + 访问的数据库 , 参数二: 用户名 , 参数三: 密码。
try {
Class.forName(driverClass);
connection = DriverManager.getConnection(url, name, password);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return connection;
}
/**
* 释放资源
* <p>Title: close</p>
* <p>Description: </p>
* @param connection
* @param resultSet
* @param statement
*/
public static void close(Connection connection,ResultSet resultSet,Statement statement){
closeRS(resultSet);
closeSt(statement);
closeConn(connection);
}
private static void closeRS(ResultSet resultSet){
try {
if(resultSet !=null){
resultSet.close();
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
resultSet = null;
}
}
private static void closeSt(Statement statement){
try {
if(statement !=null){
statement.close();
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
statement = null;
}
}
private static void closeConn(Connection connection){
try {
if(connection !=null){
connection.close();
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
connection = null;
}
}
}
运行结果:
正确示例2:
jdbc.properties在src下:
JDBCTest:
package com.test.example;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import com.mysql.jdbc.Driver;
import com.test.util.JDBCUtil;
public class JDBCTest {
public static void main(String[] args) {
// TODO Auto-generated method stub
Connection connection = null;
Statement statement = null;
ResultSet resultSet = null;
try {
//1. 注册驱动
connection = JDBCUtil.getConn();
/*
//Driver 这个类里面有静态代码块,一上来就执行了,所以等同于我们注册了两次驱动。 其实没这个必要的。
//静态代码块 ---> 类加载了,就执行。 java.sql.DriverManager.registerDriver(new Driver());
//DriverManager.registerDriver(new com.mysql.jdbc.Driver());
Class.forName("com.mysql.jdbc.Driver");
//2. 建立连接 参数一: 协议 + 访问的数据库 , 参数二: 用户名 , 参数三: 密码。
connection = DriverManager.getConnection("jdbc:mysql://localhost/jdbc", "root", "root");*/
//3. 创建statement , 跟数据库打交道,一定需要这个对象
statement = connection.createStatement();
//4. 执行查询 , 得到结果集
String sql = "select * from stu";
resultSet = statement.executeQuery(sql);
//5. 遍历查询每一条记录
while(resultSet.next()){
int id = resultSet.getInt("id");
String name = resultSet.getString("name");
int age = resultSet.getInt("age");
System.out.println("id="+id+",name="+name+",age="+age);
}
// resultSet.close();
// Statement.close();
// connection.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
JDBCUtil.close(connection, resultSet, statement);
}
}
}
JDBCUtil:
package com.test.util;
import java.io.FileInputStream;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
public class JDBCUtil {
static String driverClass = null;
static String url = null;
static String name = null;
static String password = null;
//读取jdbc.properties
static{
try {
//1.创建一个属性配置对象
Properties properties = new Properties();
//1.对应文件位于工程根目录
//InputStream is = new FileInputStream("jdbc.properties");
//2.使用类加载器,读取drc下的资源文件 对应文件位于src目录底下 建议使用
InputStream is = JDBCUtil.class.getClassLoader().getResourceAsStream("jdbc.properties");
//2.导入输入流,抓取异常
properties.load(is);
//3.读取属性
driverClass = properties.getProperty("driverClass");
url = properties.getProperty("url");
name = properties.getProperty("name");
password = properties.getProperty("password");
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
}
/**
* 注册驱动 建立参数
* <p>Title: close</p>
* <p>Description: </p>
* @param connection
* @param resultSet
* @param statement
*/
public static Connection getConn(){
Connection connection = null;
//2. 建立连接 参数一: 协议 + 访问的数据库 , 参数二: 用户名 , 参数三: 密码。
try {
Class.forName(driverClass);
connection = DriverManager.getConnection(url, name, password);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return connection;
}
/**
* 释放资源
* <p>Title: close</p>
* <p>Description: </p>
* @param connection
* @param resultSet
* @param statement
*/
public static void close(Connection connection,ResultSet resultSet,Statement statement){
closeRS(resultSet);
closeSt(statement);
closeConn(connection);
}
private static void closeRS(ResultSet resultSet){
try {
if(resultSet !=null){
resultSet.close();
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
resultSet = null;
}
}
private static void closeSt(Statement statement){
try {
if(statement !=null){
statement.close();
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
statement = null;
}
}
private static void closeConn(Connection connection){
try {
if(connection !=null){
connection.close();
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally {
connection = null;
}
}
}
jdbc.properties:
driverClass=com.mysql.jdbc.Driver
url = jdbc:mysql://localhost/jdbc
name = root
password = root
数据库:
数据库:
运行结果:
总结:
JDBCUtil:
//1.对应文件位于工程根目录 //InputStream is = new FileInputStream("jdbc.properties"); //2.使用类加载器,读取drc下的资源文件 对应文件位于src目录底下 建议使用 InputStream is = JDBCUtil.class.getClassLoader().getResourceAsStream("jdbc.properties"); |
主要是看JDBCUtil下的这两行代码,这两行代码分别对应jdbc.properties配置文件的路径.
jdbc.properties的路径是在src下还是在工程的根目录下
这两种方式都可行