使数据库确定性地失败以进行测试 [英] Make DB fail deterministically for testing

问题描述

我有一个 Java 应用程序，它使用大量 java.sql.Connection 到数据库.

I have a Java application that uses lots of java.sql.Connection to a database.

我想测试一下，如果数据库不可用，我的服务会返回适当的错误代码(区分临时问题和永久性问题，例如 HTTP 500 和 503).

I want to test that, if the database is unavailable, my services return the appropriate error codes (distinguishing between temporary and permanent problems e.g. HTTP 500 and 503).

为了测试，我的应用程序连接到嵌入式、本地、内存中的 h2 数据库；应用程序不知道这一点，只有我的集成测试是.

For testing, my application connects to an embedded, local, in-memory h2 database; the application is not aware of this, only my integration test is.

我怎样才能确定性地使写入数据库失败，例如挂钩提交并让它们抛出自定义 SQLException?我想要测试代码中的全局数据库不可用"布尔值影响所有连接并使我的应用程序执行其重新连接逻辑.

How can I make writes to the database fail deterministically, e.g. hook into commits and make them throw a custom SQLException? I want a global 'database is unavailable' boolean in the test code that affects all connections and makes my application exercise its reconnect logic.

^{(我已经开始代理 Connection 并在 commit() 中放置一个 if(failFlag) throw new MySimulateFailureException(); 但这并没有抓住 PreparedStatement.executeUpdate(); 在我开始代理 PreparedStatement 之前 - 它有很多方法！ - 我想被教导更好的方法...)}

^{(I had started by proxying Connection and putting an if(failFlag) throw new MySimulateFailureException() in commit(); but this didn't catch PreparedStatement.executeUpdate(); before I embark on proxying the PreparedStatement too - its a lot of methods! - I'd like to be taught a better way...)}

推荐答案

我最终制作了自己的 Java 反射包装器来拦截 Connection.commit 和 PreparedStatement.execute... 方法.

I ended up making my own Java reflection wrapper that intercepts Connection.commit and the PreparedStatement.execute... methods.

我在DBFactory"类中的最终代码:

My final code in my 'DBFactory' class:

@SuppressWarnings("serial")
public class MockFailureException extends SQLException {
    private MockFailureException() {
        super("The database has been deliberately faulted as part of a test-case");
    }
}

private class MockFailureWrapper implements InvocationHandler {

    final Object obj;

    private MockFailureWrapper(Object obj) {
        this.obj = obj;
    }

    @Override public Object invoke(Object proxy, Method m, Object[] args) throws Throwable {
        if(dbFailure && ("commit".equals(m.getName()) || m.getName().startsWith("execute")))
            throw new MockFailureException();
        Object result;
        try {
            result = m.invoke(obj, args);
            if(result instanceof PreparedStatement)
                result = java.lang.reflect.Proxy.newProxyInstance(
                        result.getClass().getClassLoader(),
                        result.getClass().getInterfaces(),
                        new MockFailureWrapper(result));
        } catch (InvocationTargetException e) {
            throw e.getTargetException();
        } catch (Exception e) {
            throw new RuntimeException("unexpected invocation exception: " + e.getMessage());
        }
        return result;
    }

}


public Connection newConnection() throws SQLException {
    Connection connection = DriverManager.getConnection("jdbc:h2:mem:"+uuid+";CREATE=TRUE;DB_CLOSE_ON_EXIT=FALSE");
    return (Connection)java.lang.reflect.Proxy.newProxyInstance(
            connection.getClass().getClassLoader(),
            connection.getClass().getInterfaces(),
            new MockFailureWrapper(connection));
}

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