调用JooQ DSLContext的.close（）时，什么时候关闭连接（如果有的话）？ [英] When is a Connection closed when calling JooQ DSLContext's .close(), if at all?

问题描述

这是我正在编写的使用JooQ 3.7.0的类的代码（不相关的部分已被剥离）；请注意 DSLContext 的 AutoCloseable 功能的使用：

Here is the code of a class which I am writing which uses JooQ 3.7.0 (the irrelevant parts have been stripped); note the uses of the AutoCloseable feature of DSLContext:

public final class JooqPerMethodMetricWriter
    implements PerMethodMetricWriter
{
    private static final Logger LOGGER
        = LoggerFactory.getLogger(JooqPerMethodMetricWriter.class);

    // [snip]

    private final DSLContext jooq;

    public JooqPerMethodMetricWriter(final Connection connection,
        final Instant instant)
        throws IOException
    {
        // [snip]    
        jooq = DSL.using(connection);    
    }

    private void writeCsv(final Configuration configuration)
    {
        // [snip]    

        try (
            final DSLContext context = DSL.using(configuration);
            final Reader reader = Files.newBufferedReader(csvPath);
        ) {

            final Loader<PermethodMetricsRecord> loader = context
                .loadInto(PERMETHOD_METRICS)
                .loadCSV(reader)
                .fields(PERMETHOD_METRICS.fields())
                .execute();
            LOGGER.info("{} lines stored in database", loader.stored());
        } catch (IOException e) {
            throw new RuntimeException("Cannot open CSV for reading", e);
        }
    // BREAKPOINT 1
    }

    @Override
    public void close()
        throws IOException
    {
        jooq.transaction(this::writeCsv);
        jooq.close();
        // BREAKPOINT 2
        Files.delete(csvPath);
    }
        // [snip]    
}

如果相关完全使用的数据库是PostgreSQL（9.4.x）。

If relevant at all, the database used is PostgreSQL (9.4.x).

在上面的代码中，我有两个断点。当我调试时，我看到：

In the code above, I have two breakpoints. When I debug, I see that:

• 在第一个断点 configuration.connectionProvider（）。acquire（） .isClosed（）是错误的...


• 在第二个断点处，
  jooq.configuration（）。connectionProvider（ ）.acquire（）。isClosed（）也是 假。

• at the first breakpoint, configuration.connectionProvider().acquire().isClosed() is false...
• at the second breakpoint, jooq.configuration().connectionProvider().acquire().isClosed() is also false.

我糊涂了。我作为构造函数参数收到的 Connection 怎么了？我是否需要自己 .close（）？

I'm confused. What happened to the Connection which I have received as a constructor parameter? Do I need to .close() it myself?

附带的问题，这次与 Loader 有关：我保留默认值，因此 .commitNone（）;鉴于我在事务处理中运行加载程序，如果我尝试使用 .commit< somethingElse>（）代替，例如 .commitAfter（1000）？

Side question, this time with regards to the Loader: I leave the defaults, therefore .commitNone(); given that I run the loader within a transacation, would it make a difference at all if I tried and .commit<somethingElse>() instead, for instance .commitAfter(1000)?

推荐答案

DSLContext 变为 AutoCloseable 。 DSLContext.close（） 方法的Javadoc解释了此 close（）调用的语义：

DSLContext became AutoCloseable with the Java 8 distributions of jOOQ 3.7. The DSLContext.close() method's Javadoc explains the semantics of this close() call:

如果构建此 DSLContext 时已分配了任何资源，则关闭基础资源。

Close the underlying resources, if any resources have been allocated when constructing this DSLContext.

某些 DSLContext 构造函数，例如 DSL.using（String） ， DSL.using（String，属性） 或 DSL.using（String，String，String） 分配一个连接资源，其中是 DSLContext 实现外部无法访问的。因此，必须通过此 close（）方法来进行适当的资源管理。

Some DSLContext constructors, such as DSL.using(String), DSL.using(String, Properties), or DSL.using(String, String, String) allocate a Connection resource, which is inaccessible to the outside of the DSLContext implementation. Proper resource management must thus be done via this close() method.

只有在构造 DSLContext 时分配的资源才会被释放。不是您传递给 DSLContext 的资源。就您而言，您没有在此 try-with-resources 语句中分配任何资源，因此在该语句的末尾没有任何可释放的内容：

Only resources allocated when you constructed the DSLContext will be released. Not resources that you passed to the DSLContext. In your case, you are not allocating any resources in this try-with-resources statement, so there is nothing to be released at the end of it:

try (DSLContext context = DSL.using(configuration); ...) { ... }

如果您在此处分配了新的 Connection ，则情况会有所不同：

This would be different if you allocated a new Connection right there:

try (DSLContext context = DSL.using("jdbc:h2:~/test", "sa", ""); ...) { ... }

关于您的问题：

Regarding your questions:

我很困惑。作为构造函数参数收到的Connection发生了什么情况？

I'm confused. What happened to the Connection which I have received as a constructor parameter?

没事。您必须自己控制其生命周期，因为jOOQ对连接生命周期策略一无所知。

Nothing. You must govern its lifecycle yourself as jOOQ doesn't know anything about your connection lifecycle strategy.

我是否需要.close（）它

Do I need to .close() it myself?

是的。

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