标签:lang JDBC java rs static import null properties
网上好像都说的是写不写 getClassLoader(),但我无论要不要这个方法都初始化不了。经过好几天折腾,发现与之无关,应该是:
具体代码如下(可以拷贝了试试,我用的是mysql 8.0.26):
db.properties:
driver= com.mysql.cj.jdbc.Driver
url = jdbc:mysql://localhost:3306/myfirst?useUnicode=true&characterEncoding=UTF-8&useSSL=true&serverTimezone=UTC
username = root
password = *****
JdbcUtils:
package JDBC;
import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;
public class JdbcUtils {
private static String driver = null;
private static String url = null;
private static String username = null;
private static String password = null;
static {
try {
InputStream in = JdbcUtils.class.getClassLoader().getResourceAsStream("db.properties");
Properties properties = new Properties();
properties.load(in);
driver = properties.getProperty("driver");
url = properties.getProperty("url");
username = properties.getProperty("username");
password = properties.getProperty("password");
Class.forName(driver);
} catch (IOException | ClassNotFoundException e) {
e.printStackTrace();
}
}
//获取连接
public static Connection getConnection() throws SQLException {
return DriverManager.getConnection(url,username,password);
}
//释放连接资源
public static void release(Connection conn, Statement st, ResultSet rs){
if(rs != null){
try {
rs.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
if(st != null){
try {
st.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
if(conn != null){
try {
conn.close();
} catch (SQLException throwables) {
throwables.printStackTrace();
}
}
}
}
Testdemo2:
package JDBC;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class Testdemo2 {
public static void main(String[] args) {
Connection conn = null;
Statement st = null;
ResultSet rs = null;
try {
conn = JdbcUtils.getConnection();//获取数据库连接
st = conn.createStatement();//获取SQL的连接对象
String sql = "select * from student";
rs = st.executeQuery(sql);
while (rs.next()){
System.out.println(rs.getObject("id"));
System.out.println(rs.getObject("name"));
System.out.println(rs.getObject("age"));
System.out.println(rs.getObject("email"));
}
} catch (SQLException throwables) {
throwables.printStackTrace();
}finally {
JdbcUtils.release(conn,st,rs);
}
}
}
标签:lang,JDBC,java,rs,static,import,null,properties 来源: https://www.cnblogs.com/Sunwell123/p/15149790.html
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