自定義ClassLoader加載mysql驅動

背景：最近在研究自定義類加載器ClassLoader加載自定義目錄的jar時，當加載mysql驅動時總是報ClassNotFoundException。

原因：當DriverManager加載驅動時只承認當前系統的加載器加載的jar，自定義的顯然不承認。

3、解決辦法：

自定義myDriver實現Driver接口，並實現接口方法，其包含成員變量Driver即可。

public class MyDriver implements Driver {
    public MyDriver(Driver driver) {
        this.driver = driver;
    }

    private Driver driver;

    @Override
    public Connection connect(String url, Properties info) throws SQLException {
        return this.driver.connect(url, info);
    }

    @Override
    public boolean acceptsURL(String url) throws SQLException {
        return this.driver.acceptsURL(url);
    }

    @Override
    public DriverPropertyInfo[] getPropertyInfo(String url, Properties info) throws SQLException {
        return this.driver.getPropertyInfo(url, info);
    }

    @Override
    public int getMajorVersion() {
        return this.driver.getMajorVersion();
    }

    @Override
    public int getMinorVersion() {
        return this.driver.getMinorVersion();
    }

    @Override
    public boolean jdbcCompliant() {
        return this.driver.jdbcCompliant();
    }

    @Override
    public Logger getParentLogger() throws SQLFeatureNotSupportedException {
        return null;
    }
}

Driver driver = null;// (Driver)app.newInstance();

        try {
             driver = (Driver) Class.forName("com.mysql.jdbc.Driver",true,paveClassLoader)
                        .newInstance();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }

DriverManager.registerDriver( new MyDriver(driver) );
Connection conn = DriverManager.getConnection(url, user, password);

以上即全部過程。

小插曲：在利用conn查詢時遇到java.sql.SQLException: Before start of result set異常，這個是因爲沒有調用rs.next()方法導致，需要每次調用rs.getxxx()前都要使cursorPos向前移動1步。