小编Jin*_*won的帖子

我现在正在这样做.

final CriteriaBuilder builder = ...;
final boolean flag = ...;

if (flag) {
    builder.isTrue(expression);
} else {
    builder.isFalse(expression);
}

我能这样用吗？

builder.equals(expression, flag);

这尝试不会有任何问题吗？对表达式或其他东西说null.

我想我刚刚发现两个不同的JPA实现在约束违规和回滚方面的工作方式不同.

@Test(expectedExceptions = @@.class) // CVE or RB?
public void testXXX() {
    final EntityManager manager = LocalPU.createEntityManager();
    try {
        final EntityTransaction transaction = manager.getTransaction();
        transaction.begin();
        try {
            manager.persist(<wrong>); // this is where CVE coming from
            transaction.commit();     // this is where RB coming from
        } catch (RollbackException re) {
            // <---------------------------------------- hibernate here
            throw re;
        } catch (ConstraintViolationException cve) {
            // <---------------------------------------- eclipselink here
            transaction.rollback();
            throw cve;
        } catch (Exception e) {
            transaction.rollback();
            e.printStackTrace(System.err);
            Assert.fail(e.getMessage());
        }
    } finally {
        manager.close();
    } …

我学习了两种创建泛型数组的方法.

一个是

@SuppressWarnings("unchecked")
static <T> T[] array1(final Class<T> elementType, final int size) {

    return (T[]) Array.newInstance(elementType, size);
}

另一个是

static <T> T[] array2(final Class<T[]> arrayType, final int size) {

    return arrayType.cast(Array.newInstance(arrayType.getComponentType(), size));
}

哪个更好？它们是相同的(内部)吗？有没有什么事实错？

如何使用Bouncy Castle生成对称密钥？无论PrivateKeyFactory和PublicKeyFactory似乎与AsymmetricKeyParameter.

我不想知道任何JCA/JCE API - 相反,我只对Bouncy Castle特定的API感兴趣.

可以(应该)我只生成一个随机字节？

假设我有一个注释。

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface MyAnnotation {
    int value() default 1;
}

有什么方法可以获取1使用反射之类的价值吗？

我延长了QWebEngineView.

#ifndef MYQWEBENGINEVIEW_H
#define MYQWEBENGINEVIEW_H
#include <QWebEngineView>
class MyQWebEngineView : public QWebEngineView
{
public:
    MyQWebEngineView(QWidget *parent = 0);
    ~MyQWebEngineView();
protected:
    virtual void paintEvent(QPaintEvent *);
};
#endif // MYQWEBENGINEVIEW_H

但我不能被paintEvent(QPaintEvent *)召唤.

#include "myqwebengineview.h"
#include <QPaintEvent>
#include <QPainter>
#include <QWebEngineView>
#include <QWidget>

MyQWebEngineView::MyQWebEngineView(QWidget *parent):QWebEngineView(parent)
{
    qDebug() << "MyQWebEngineView(" << parent << ")";
    qDebug() << "Qt::WA_PaintOnScreen: " << testAttribute(Qt::WA_PaintOnScreen);
    //setAttribute(Qt::WA_PaintOnScreen, true);
}
MyQWebEngineView::~MyQWebEngineView()
{
}
void MyQWebEngineView::paintEvent(QPaintEvent * event)
{
    qDebug() << "paintEvent(" << event << ")";
    QWebEngineView::paintEvent(event);
    //QWidget::paintEvent(event); …

用a Stream<T>和a Comparator<? super T>,

Stream<T> s;
Comparator<? super T> c;

是

s.sorted(c).findFirst();

等于相当于

s.min(c);

？

我是leiningen的新手.

当我试图执行以下时,

$ lein clean jar

我有

Wrong number of arguments to clean task. 
Expected []
$ 

如何在一个命令中执行多个任务？

我知道这Pageable来自spring-data-域名.

有没有直接使用任何优雅的方式org.springframework.data.domain.Pageable在@RestController？

我试过跟随.

@RequestMapping(method = RequestMethod.GET,
                path = "pageable",
                produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<Pageable> readPageable(@NotNull final Pageable pageable) {
    return ResponseEntity.ok(pageable);
}

结果不是我的预期.

...: ~ $ curl -X GET --header 'Accept: application/json' 'http://localhost:8080/.../pageable?limit=1&offset=1' | python -mjson.tool
...
{
    "offset": 0,
    "pageNumber": 0,
    "pageSize": 20,
    "sort": null
}

我试图扩展,TemporalAdjuster以便看起来像,

public interface TypedTemporalAdjuster<T extends Temporal & Comparable<? super T>> {

    T adjustInto(T temporal);
}

当我试图直接扩展基接口时,

public interface TypedTemporalAdjuster<T extends Temporal & Comparable<? super T>>
        extends TemporalAdjuster {

    T adjustInto(T temporal);
}

我收到了一个错误.

... java:name clash:...有相同的擦除,但都没有覆盖另一个

有没有办法做到这一点？

到目前为止,我做到了.

public interface TypedTemporalAdjuster<T extends Temporal & Comparable<? super T>> { //extends TemporalAdjuster {

    static <T extends Temporal & Comparable<? super T>> TypedTemporalAdjuster<T> of(
            final Class<T> temporalClass, final TemporalAdjuster temporalAdjuster) {
        return temporal -> temporalClass.cast(temporalAdjuster.adjustInto(temporalClass.cast(temporal)));
    }

    T adjustInto(T temporal);
}