小编Rom*_*Kap的帖子

我正在尝试加载pictureA或pictureB.我的第一个解决方案是这样的:

 <img *ngIf="my_picture" src="{{my_picture}}" width="180" height="80" >
 <img *ngIf="default_picture && !my_picture" src="{{default_picture}}">

但我想使用if- else就像API参考:

<div *ngIf="condition; else elseBlock">...</div>
<ng-template #elseBlock>...</ng-template>

所以,我试着这样做:

 <div *ngIf="my_picture; else elseBlock">
     <img src="{{my_picture}}" >
 </div>
 <ng-template #elseBlock>
      <img src="{{default_picture}}" >
 </ng-template>

但是我得到了一个很大的异常堆栈跟踪:

zone.js:388 Unhandled Promise rejection: Template parse errors:
Can't bind to 'ngIfElse' since it isn't a known property of 'div'. ("
        -->

        <div [ERROR ->]*ngIf="my_picture; else elseBlock">
            <img src="{{my_picture}}"): UserComponent@15:13
Property binding ngIfElse not used by any directive …

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我习惯用plattform-b​​rowser-dynamic 2.0.0导入bootstrap,如下所示:

import { bootstrap } from '@angular/platform-browser-dynamic/';

现在我创建新的Projekt并使用角度版本2.2.0 Plattform-b​​rowser-dynamic packages具有版本2.2.0:

 "@angular/common": "~2.2.0",
    "@angular/compiler": "~2.2.0",
    "@angular/core": "~2.2.0",
    "@angular/forms": "~2.2.0",
    "@angular/http": "~2.2.0",
    "@angular/platform-browser": "~2.2.0",
    "@angular/platform-browser-dynamic": "~2.2.0",
    "@angular/router": "~3.2.0",
    "@angular/upgrade": "~2.2.0",
    "angular-in-memory-web-api": "~0.1.15"

我尝试使用包2.0.0导入bootstrap,但是找不到它.我的代码:

import { bootstrap } from '@angular/platform-browser-dynamic/*';
import {AppComponent} from "./app.component";
bootstrap(AppComponent);

错误:

错误TS2305:模块'"../ node_modules/@angular/platform-b​​rowser-dynamic/index"'没有导出成员'bootstrap'.

我该如何解决这个问题？我找不到类似的lib.

我正面临着有趣的 LazyInitializationException 解决方案。为了防止这种情况（在 OneToMany 或 ManyToMany 上），一种已知的解决方案是使用 JOIN FETCH Query。你可以看到她的几个例子之一：https ://thoughts-on-java.org/best-practices-for-many-to-many-associations-with-hibernate-and-jpa/

其他更简单的解决方案是使用 Spring 中的 @Transactional。例如像这样：

@DeleteMapping(value ="/product/{tagId}")
    @ResponseBody
    @Transactional
    public String deleteProductWithoutRelation(@PathVariable String product, Model model) {     
        Optional<Product> pr = productService.selectProduct(product);
        if (pr.isPresent()) {
            tag.get().getCustomer().size(); //usualy throws LazyInitializationException, 
                                            //without JOIN-FETCH Statment or @Transactional
        return deletedTagId;    
    }

当然，您可以在存储库服务中放置一些方法的@Transactional，以封装此解决方案。那么这两种解决方案的优点或缺点是什么？