Android Studio 连接 MySQL数据库

标签：String rs new static MySQL Studio Android null public

1、下载MySQL-connector-jave.jar包

地址如下：https://mvnrepository.com/artifact/mysql/mysql-connector-java/5.1.46

 

2、将jar包移到如图所示的位置，然后右键 add as library

 

 

3、在AndroidManifest.xml里面添加如下代码：

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

 

 4、新建一个工具类 DBUtils 用于连接数据库

public class DBUtil {

    private final static String driver = "com.mysql.jdbc.Driver";
    private final static String url = "jdbc:mysql://本机的IP地址:3306/leave_application_system?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC";
    private final static String username = "root";
    private final static String password = "你的密码";

    Connection conn=null;
    Statement st=null;
    ResultSet rs=null;

    static {
        try {
            Class.forName(driver);
        } catch (ClassNotFoundException e) {
            System.out.println("加载驱动错误");
        }
    }

    //2. 获取连接
    public static Connection getConnect() throws Exception {
        return DriverManager.getConnection(url, username, password);
    }

    //3. 释放连接资源
    public static void release(Connection conn, Statement st, ResultSet rs) throws Exception {
        if (rs != null) {
            rs.close();
        }
        if (st != null) {
            st.close();
        }
        if (conn != null) {
            conn.close();
        }

    }

}

 注意不能使用localhost代替本机的IP地址，因为Android虚拟机连接MySQL数据库 需要 本机的ip地址，否则会报错

 

5、新建类 Dao 用于对数据进行操作. （以UserDao为例）

public class UserDao {
    private DBUtil DBUtils;

    //查询用户的方法
    public boolean select(String username, String password, String role) throws Exception {
        Connection conn = null;
        Statement state = null;
        ResultSet rs = null;
        try {
            conn = DBUtils.getConnect();
            state = conn.createStatement();
            String sql = "select * from user where userNo = '" + username + "' and password = '" + password + "' and role ='" + role + "'";
            System.out.println(sql);
            rs = state.executeQuery(sql);
            if(rs.next()){
                return true;
            }else{
                return false;
            }
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        } finally {
            DBUtils.release(conn, state, rs);
        }
    }
}

 

6、在Android 的 Activity类中调用上面的Dao类对象，进行数据操作 （以登录为例）button1.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                Thread thread = new Thread() {
                    public void run() {
                        UserDao userDao = new UserDao();
                        String userNo = text1.getText().toString();
                        String password = text2.getText().toString();
                        try {
                            Message msg = new Message();
                            Bundle bundle = new Bundle();

                            bundle.putString("result", String.valueOf(userDao.select(userNo, password, ROLE)));
                            msg.setData(bundle);
　　　　　　　　　　　　　　　　//将查询得到的结果通过handler异步发送给主线程
                            handler.sendMessage(msg);
                        } catch (IOException ex) {
                            ex.printStackTrace();
                            String result = ex.toString();
                            Message msg = new Message();
                            Bundle bundle = new Bundle();
                            bundle.putString("result", result);
                            msg.setData(bundle);
                            handler.sendMessage(msg);
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
                };
                thread.start();
            }
        });

}
    private void initHandlers(){
        handler = new Handler() {
            @Override
            public void handleMessage(Message msg) {
                String result = msg.getData().getString("result");
              /.../
        };
    }

 注意调用Dao类的代码（即JDBC连接数据库）不能放在主线程上，不然就会报错。上面使用thread创建线程，在线程中进行数据操作。

 

问题：

java.lang.NoClassDefFoundError: Failed resolution of: Ljava/sql/SQLType;

解决方法：

如果你的jar包版本为8，将jar包的版本降低，我使用的是5.1.46版本

注意此时的配置代码为：

private final static String driver = "com.mysql.jdbc.Driver";
private final static String url = "jdbc:mysql://10.81.98.193:3306/leave_application_system?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC";

 

 

 

 

 

 

 

 

 

标签：String,rs,new,static,MySQL,Studio,Android,null,public
From： https://www.cnblogs.com/yccy/p/16916481.html