Question

我有一个名为“ VirtuellTx”的可自动关闭的类。它是一种特殊的事务，并支持“ commit（）”和“ rollback（）”方法。如何访问catch块中声明的“ VirtuellTx”资源以执行rollback（）？

try (VirtuellTx lVtx = new VirtuellTx()) {
    // do something ...
    lVtx.commit();
} catch (Exception e) {
    lVtx.rollback();
}

catch块无法访问lVtx：“ lVtx无法解析”

Answer 1

资源仅在try-with-resources语句块的范围内。 JLS says：

在try-with-resources语句（第14.20.3节）的ResourceSpecification中声明的变量的作用域是从声明开始，到ResourceSpecification的其余部分以及与try-with-resources相关联的整个try块。声明。

将catch移到内部：

try (VirtuellTx lVtx = new VirtuellTx()) {
  try {
    // do something ...
    lVTX.commit();
  } catch (Exception e) {
    lVtx.rollback();
  }
}

Answer 2

我已经对自己的工作进行了测试，可以使用多种方法，请检查哪种方法适合您的要求。我找到了很好的参考资料，并举例说明了该问题，参考链接：http://tutorials.jenkov.com/java-exception-handling/try-with-resources.html

 public class AutoClosableResource implements AutoCloseable {

private String   name                 = null;
private boolean throwExceptionOnClose = false;

public AutoClosableResource(String name, boolean throwExceptionOnClose) {
    this.name = name;
    this.throwExceptionOnClose = throwExceptionOnClose;
}

public void doOp(boolean throwException) throws Exception {
    System.out.println("Resource " + this.name + " doing operation");
    if(throwException) {
        throw new Exception("Error when calling doOp() on resource " + this.name);
    }
}

@Override
public void close() throws Exception {
    System.out.println("Resource " + this.name + " close() called");
    if(this.throwExceptionOnClose){
        throw new Exception("Error when trying to close resource " + this.name);
    }
}}

另一种方法

public static void tryWithResourcesSingleResource() throws Exception {
try(AutoClosableResource resourceOne = new AutoClosableResource("One", true)) {
    resourceOne.doOp(false);
} catch(Exception e) {
    Throwable[] suppressed = e.getSuppressed();
    throw e;
} finally {
    throw new Exception("Hey, an exception from the finally block");
}}

访问在捕获子句中声明为“ try-with”资源

2 个答案: