使用JDBC将Android应用程序连接到Bluemix db2数据库（noClassDefFounderRor：）

Question

代码：

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import java.sql.*;
public class MainActivity extends AppCompatActivity {

static Connection       con;
static Statement        stmt;
static Statement        stmt1;
static DatabaseMetaData dmd;


private static String user = "user*****";
private static String password = "L***********";
private static String url = "jdbc:db2://*.**.*****:50001/SQLDB";


public void connect(){
    java.util.Properties properties = new java.util.Properties();

    properties.put("user", user);
    properties.put("password", password);
    properties.put("sslConnection", "true");

    try {
        Class.forName("com.ibm.db2.jcc.DB2Driver");
    con = DriverManager.getConnection(url, properties);
    stmt = con.createStatement();

    } catch (ClassNotFoundException e) {
       // e.printStackTrace();
    } catch (SQLException e) {
      //  e.printStackTrace();
    }
}
public void close() throws SQLException, ClassNotFoundException{
    stmt.close();
    con.close();
}

public static void addSomethingToMyToDoList(int ID, String something) throws SQLException{
    if(con != null)
        stmt.executeUpdate("INSERT INTO TODOLIST VALUES (" + ID + " , '" + something +"')");
    con.commit();
}

public void addSomethingToDatabase(View v){
    connect();
    int sampleID = 1233;
    try {
        addSomethingToMyToDoList(sampleID, "testTest");
         close();
    } catch (SQLException e) {
        e.printStackTrace();
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}
}

我将db2jcc.jar拖放到/app/libs文件夹中，并右键单击+Add as library

我使用Android Studio

我读到db2jcc.jar不能与jdk 1.8一起工作，这就是我安装jdk 1.7的原因（Did file->project structure->SDK Location->将jdk Location更改为我的JDK1.7.0目录）

build.gradle文件包含：

defaultConfig {
    [...]
    multiDexEnabled true
}
dependencies {
compile fileTree(include: ['*.jar'], dir: 'libs')
compile files('libs/db2jcc.jar')
testCompile 'junit:junit:4.12'
compile 'com.android.support:design:23.1.1'
compile 'com.android.support:multidex:1.0.1'
compile 'com.android.support:appcompat-v7:23.1.1'
}

当我运行我的应用程序（在AVD上）并点击按钮时，我的应用程序会显示一条消息：

Caused by: java.lang.NoClassDefFoundError: com.ibm.db2.jcc.DB2SimpleDataSource

完整错误日志：

Class.forName("com.ibm.db2.jcc.DB2Driver").newInstance();

Class.forName("com.ibm.db2.jcc.DB2Driver");

谢谢。

Answer 1

错误很明显，您的应用程序找不到db2模块。检查是否正确地将这些模块导入到应用程序库中，并且添加到lib中的驱动程序是否提供了用于DataSource的类。

无论如何，我会避免让您的应用程序直接连接到外部数据库，原因有几个：

• db连接通常是有限的，将它们用于每个应用程序实例将使db实例很快失去可用连接，特别是如果db交互不是很短，而且连接没有正确释放
• 便携式设备的网络连接不稳定，在运行数据库操作时可能会失去连接