数据库连接Java

数据库选择了mysql，首先下载MySQL
https://dev.mysql.com/downloads/installer/
选择下面一个不是web的

然后下载JDBC
https://dev.mysql.com/downloads/connector/j/
还是选下面一个

下载好之后，把jar包放入jdk的lib文件夹中，并在环境变量classpath添加%JAVA_HOME%\lib\mysql-connector-java-5.1.44-bin.jar（对应名称）
然后就可以打开eclipse啦

首先创建项目，右击选择Build Path，configure build path，然后add external JARs,选择jar包，否则报错。
可以开始写啦
nope，首先要在mysql建库建表，这里我的数据库叫javalinkmysql，表叫test，然后插入了几行数据。然后就可以开始啦。

import java.sql.*;//导入包
public class DBtest {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
          String driver = "com.mysql.jdbc.Driver";
            String url = "jdbc:mysql://127.0.0.1:3306/javalinkmysql?useUnicode=true&characterEncoding=utf-8&useSSL=false";
            String user = "root";
            String password = "1002482382";
            try{
                Class.forName(driver);
                Connection connection = DriverManager.getConnection(url,user,password);
                if(!connection.isClosed()){
                    System.out.println("连接成功");
                }
                Statement statement = connection.createStatement();
                String sql = "select * from test";
                ResultSet result = statement.executeQuery(sql);
                while(result.next()){
                    System.out.print(result.getString("id")+" ");
                    System.out.print(result.getString("name")+" ");
                    System.out.print(result.getString("gender")+" ");
                    System.out.println(result.getString("age"));
                }
                result.close();
                connection.close();
            }catch(Exception e){
                e.printStackTrace();
            }
    }

}

这里要注意

String url = "jdbc:mysql://127.0.0.1:3306/javalinkmysql?useUnicode=true&characterEncoding=utf-8&useSSL=false";

javalinkmysql是database的名称，
?useUnicode=true&characterEncoding=utf-8&useSSL=false”
是因为警告

Sun Sep 10 16:15:13 CST 2017 WARN: Establishing SSL connection without server’s identity verification is not recommended. According to MySQL 5.5.45+, 5.6.26+ and 5.7.6+ requirements SSL connection must be established by default if explicit option isn’t set. For compliance with existing applications not using SSL the verifyServerCertificate property is set to ‘false’. You need either to explicitly disable SSL by setting useSSL=false, or set useSSL=true and provide truststore for server certificate verification.

链接成功，显示数据。

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