通过表单传递的元素不会被服务器接收，也不会显示在前面.修补方法|角度| Dropwizard [英] Elements passed through a form not received by the server nor displayed on the front. PATCH method | Angular | Dropwizard

问题描述

服务器端显示调用了PATCH方法，并在数组末尾添加了一个null，而不是使用名称和价格来自用户输入的新Item数组.

Server side shows that the PATCH method is called and adds a null at the end of the array, instead of a new Item array with the Name and Price taken from user input.

PATCH方法:

      patchAdd(menu: MenuModel | number, itemToAdd: ItemClass): Observable<any> { 
        const id = typeof menu === 'number' ? menu: menu.id;
        const url = `${this.menusUrl}/add/${id}`;

        return this.http.patch(url, itemToAdd, httpOptions).pipe ()
}

patchItAdd函数，该函数实现patchAdd方法并从html中获取数据.请注意，由于尝试不成功，有一些注释.

patchItAdd function which implements the patchAdd method and takes data from html: Note that there are a couple of comments, from my unsuccessful tries.

 patchItAdd(name: string, price: number){
        name = name.trim();
        if (!name) {return;}
        const id = +this.route.snapshot.paramMap.get('id');
        this.menuService.patchAdd(id, this.item)
        //With this ^^ , the value is null, but new element is added to the array. Cannot read property push of undefined. PATCH is triggered on the backend.
        // this.menuService.patchAdd(id, {name, price} as ItemClass) ----- Three errors, nothing happens
        .subscribe(item => {
          this.items.push(item);
        });}

用于收集用户输入并将数据传递给功能的HTML标签:

<label class="forma">
          Name of the item:
          <input #itemName placeholder="What's the name of the item?" onfocus="this.placeholder =''" onblur="this.placeholder = 'What\'s the name of the item?'"/><br><br>
          Item's price:
          <input #itemPrice placeholder="What's the price?"onfocus="this.placeholder =''" onblur="this.placeholder = 'What\'s the price?'"/><br><br>
          <span class="addnewbuttontext"><button class="addnewitembutton" (click) = "patchItAdd(itemName.value, itemPrice.value)">Add</button></span>
      </label><br>

后端(Dropwizard)中的

PATCH方法:

PATCH method in the backend (Dropwizard):

   @PATCH
   @Path("/add/{menuId}")
   public void addMenuItem(
            @PathParam("menuId") final int menuId,
            final Item item) {  
      final java.util.List<Item> items = this.menuRepository.get(menuId).getItems();
      items.add(item);
   }

在单击"ADD"按钮并调用patchItAdd函数之后，仅将null添加到后端的数组.显然，因此也没有数据显示在前端.我在做什么错，或者至少应该如何使用Angular 7在前端使用PATCH方法?

Only a null is added to the array on the backend after clicking the "ADD" button and calling the patchItAdd function. Obviously, no data is displayed on the front-end neither because of that. What am I doing wrong, or at least how should I approach the PATCH method on the front-end, with Angular 7?

推荐答案

即使我对问题没有完全的了解，我也会尝试解决两点.

I'll try to address a couple of points, even if I don't have a complete understanding of the problem.

为什么要在其中放置+?它将以数字表示形式转换变量，这就是您想要的吗? get()调用返回值是string | null

Why are putting a + there? It will transform the variable in its numeric representation, is that what you want? The get() call return value is string | null

const id = +this.route.snapshot.paramMap.get('id');

---

这里您要使用this.item调用menuService.patchAdd，但是我想您想使用输入值name和price创建一个新的Item实例.

---

Here you're calling menuService.patchAdd with this.item, but I suppose you want to create a new Item instance using the input values name and price.

// Angular
(click) = patchItAdd(itemName.value, itemPrice.value)

// Java
patchItAdd(name: string, price: number){
     ...
     this.menuService.patchAdd(id, this.item)

我的假设正确吗?

我看到的另一个问题是您正在将id传递给patchAdd id应该是string(或您的情况下的number，因为您使用+进行了转换)

Another issue I see is that you're passing the id, which should be string (or number in your case, since you transform it with the +) to patchAdd

const id = +this.route.snapshot.paramMap.get('id');
this.menuService.patchAdd(id, this.item)

patchAdd函数需要一个MenuModel，它是一个复杂的对象.
怎么样?您确定这就是您想要的吗?

The patchAdd function expect a MenuModel, which is a complex object.
How's that? Are you sure this is what you want?

让patchItAdd接受menu.id值

(click) = "patchItAdd(menu.id, itemName.value, itemPrice.value)"

现在更新方法

// Now this method accept the MenuModel#id property
patchItAdd(menuId: number, name: string, price: number){
   if (!name) {
      return;
   }

   const trimmedName = name.trim();

   // Construct a new ItemClass instance.
   // You need to take care by yourself of the "person" property and the "quantity" property
   const newItem = new ItemClass("", trimmedName, 0, price)

   this.menuService.patchAdd(menuId, newItem).subscribe(item => {
      this.items.push(item);
   });
}

也更新patchAdd方法以接受菜单ID，而不是完整的MenuModel

Update also the patchAdd method to accept the menu ID, instead of the complete MenuModel

// Now this method accepts the menu ID  
patchAdd(menuId: number, itemToAdd: ItemClass): Observable<any> { 
   const url = `${this.menusUrl}/add/${menuId}`
   return this.http.patch(url, itemToAdd, httpOptions)
}

在后端向Item

public Item() { }

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