学生宿舍管理系统（jsp+mysql）.rar

Java学生宿舍管理系统，技术架构方面使用jsp+mysql。源代码和数据库脚本齐全。有运行截图。适合大学生毕业设计参考和Java的初步学习者使用。

文件下载：n459.com/file/25127180-476645687

以下内容无关：

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刚开始写views.py模块的代码，一般都是用def定义的函数视图，不过DRF更推荐使用class定义的类视图，这能让我们的代码更符合DRY（Don’t Repeat Yourself）设计原则：

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使用APIView rest_framework.views.APIView是DRF封装的API视图，继承了django.views.generic.base.View：

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我们用它把函数视图改写成类视图，编辑snippets/views.py： from snippets.models import Snippet from snippets.serializers import SnippetSerializer from django.http import Http404 from rest_framework.views import APIView from rest_framework.response import Response from rest_framework import status

class SnippetList(APIView): “”" List all snippets, or create a new snippet. “”" def get(self, request, format=None): snippets = Snippet.objects.all() serializer = SnippetSerializer(snippets, many=True) return Response(serializer.data)

def post(self, request, format=None):
    serializer = SnippetSerializer(data=request.data)
    if serializer.is_valid():
        serializer.save()
        return Response(serializer.data, status=status.HTTP_201_CREATED)
    return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
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class SnippetDetail(APIView): “”" Retrieve, update or delete a snippet instance. “”" def get_object(self, pk): try: return Snippet.objects.get(pk=pk) except Snippet.DoesNotExist: raise Http404

def get(self, request, pk, format=None):
    snippet = self.get_object(pk)
    serializer = SnippetSerializer(snippet)
    return Response(serializer.data)

def put(self, request, pk, format=None):
    snippet = self.get_object(pk)
    serializer = SnippetSerializer(snippet, data=request.data)
    if serializer.is_valid():
        serializer.save()
        return Response(serializer.data)
    return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

def delete(self, request, pk, format=None):
    snippet = self.get_object(pk)
    snippet.delete()
    return Response(status=status.HTTP_204_NO_CONTENT)
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类视图的代码跟函数视图是非常类似的，区别在于GET、POST等方法是用的函数而不是if语句，可以更好的解耦代码。

改了views.py代码后，需要同时修改snippets/urls.py：

from django.urls import path from rest_framework.urlpatterns import format_suffix_patterns from snippets import views

urlpatterns = [ path(‘snippets/’, views.SnippetList.as_view()), path(‘snippets/int:pk/’, views.SnippetDetail.as_view()), ]

urlpatterns = format_suffix_patterns(urlpatterns) 为什么要加个as_view()方法？

因为path()的参数必须是可调用的，在源码中能看到elif callable(view)：

def _path(route, view, kwargs=None, name=None, Pattern=None): if isinstance(view, (list, tuple)): # For include(…) processing. pattern = Pattern(route, is_endpoint=False) urlconf_module, app_name, namespace = view return URLResolver( pattern, urlconf_module, kwargs, app_name=app_name, namespace=namespace, ) # callable判断 elif callable(view): pattern = Pattern(route, name=name, is_endpoint=True) return URLPattern(pattern, view, kwargs, name) else: raise TypeError(‘view must be a callable or a list/tuple in the case of include().’) as_view()方法返回了一个内部定义的可调用函数：

@classonlymethod def as_view(cls, **initkwargs): “”“Main entry point for a request-response process.”"" for key in initkwargs: if key in cls.http_method_names: raise TypeError( 'The method name %s is not accepted as a keyword argument ’ ‘to %s().’ % (key, cls.name) ) if not hasattr(cls, key): raise TypeError("%s() received an invalid keyword %r. as_view " "only accepts arguments that are already " “attributes of the class.” % (cls.name, key))

# 内部定义了可调用函数
def view(request, *args, **kwargs):
    self = cls(**initkwargs)
    self.setup(request, *args, **kwargs)
    if not hasattr(self, 'request'):
        raise AttributeError(
            "%s instance has no 'request' attribute. Did you override "
            "setup() and forget to call super()?" % cls.__name__
        )
    return self.dispatch(request, *args, **kwargs)
view.view_class = cls
view.view_initkwargs = initkwargs

# take name and docstring from class
update_wrapper(view, cls, updated=())

# and possible attributes set by decorators
# like csrf_exempt from dispatch
update_wrapper(view, cls.dispatch, assigned=())
return view
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使用mixins DRF提供了rest_framework.mixins模块，封装了类视图常用的增删改查方法：

比如新增CreateModelMixin：

class CreateModelMixin: “”" Create a model instance. “”" def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) self.perform_create(serializer) headers = self.get_success_headers(serializer.data) return Response(serializer.data, status=status.HTTP_201_CREATED, headers=headers)

def perform_create(self, serializer):
    serializer.save()

def get_success_headers(self, data):
    try:
        return {'Location': str(data[api_settings.URL_FIELD_NAME])}
    except (TypeError, KeyError):
        return {}
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类视图继承了Mixin后，可以直接使用它的.create()方法，类似的还有.list()、.retrieve()、.update()和.destroy()。我们按照这个思路来简化snippets/views.py代码：

from snippets.models import Snippet from snippets.serializers import SnippetSerializer from rest_framework import mixins from rest_framework import generics

class SnippetList(mixins.ListModelMixin, mixins.CreateModelMixin, generics.GenericAPIView): queryset = Snippet.objects.all() serializer_class = SnippetSerializer

def get(self, request, *args, **kwargs):
    return self.list(request, *args, **kwargs)

def post(self, request, *args, **kwargs):
    return self.create(request, *args, **kwargs)
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class SnippetDetail(mixins.RetrieveModelMixin, mixins.UpdateModelMixin, mixins.DestroyModelMixin, generics.GenericAPIView): queryset = Snippet.objects.all() serializer_class = SnippetSerializer

def get(self, request, *args, **kwargs):
    return self.retrieve(request, *args, **kwargs)

def put(self, request, *args, **kwargs):
    return self.update(request, *args, **kwargs)

def delete(self, request, *args, **kwargs):
    return self.destroy(request, *args, **kwargs)
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瞬间少了好多代码，真够DRY的。

什么是mixin？

维基百科的解释：

In object-oriented programming languages, a mixin (or mix-in) is a class that contains methods for use by other classes without having to be the parent class of those other classes. 不太好理解。

换句话说，mixin类提供了一些方法，我们不会直接用这些方法，而是把它添加到其他类来使用。

还是有点抽象。

再简单点说，mixin只不过是实现多重继承的一个技巧而已。

这下应该清楚了。

使用generics 如果仔细看snippets/views.py的代码，就会发现我们用到了from rest_framework import generics：

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和generics.GenericAPIView：

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这是DRF提供的通用API类视图，mixins只提供了处理方法，views.py中的类要成为视图，还需要继承GenericAPIView，GenericAPIView继承了本文第一小节提到的rest_framework.views.APIView。除了GenericAPIView，我们还可以用其他的类视图进一步简化代码：

from snippets.models import Snippet from snippets.serializers import SnippetSerializer from rest_framework import generics

class SnippetList(generics.ListCreateAPIView): queryset = Snippet.objects.all() serializer_class = SnippetSerializer

class SnippetDetail(generics.RetrieveUpdateDestroyAPIView): queryset = Snippet.objects.all() serializer_class = SnippetSerializer 看看ListCreateAPIView的源码：

class ListCreateAPIView(mixins.ListModelMixin, mixins.CreateModelMixin, GenericAPIView): “”" Concrete view for listing a queryset or creating a model instance. “”" def get(self, request, *args, **kwargs): return self.list(request, *args, **kwargs)

def post(self, request, *args, **kwargs):
    return self.create(request, *args, **kwargs)
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真DRY！

东方说 学到这里，已经开始感受到了Django REST framework的强大之处了，我觉得学一个框架，不仅要看如何使用，还需要了解它的设计思路和底层实现，这样才能更好的总结为自己的编程思想，写出更漂亮的代码。