AngularX Http服务总结

自己经常用的方式：

1.首先看httpModule

　　Angular2的http访问经常采用两种方式：

　　共同点：导入相应的Module

import {Http, RequestOptions, Response} from '@angular/http';

　　在module文件中配置

import {HttpModule} from '@angular/http';

imports: [ // import Angular's modules
    BrowserModule,
    BrowserAnimationsModule,
    HttpModule,

　　在service的构造器中进行注入

constructor(private http: Http) {
    super();
  }

1.1 用promise实现服务层返回

 // 获取设置
  public getOptions(): Promise<any> {
    return this.http
      .get(this._optionApiUrl)
      .toPromise()
      .then((res: Response) => res.json())
      .catch((error: any) => Observable.throw(error || 'Server error'));
  }

其中then里面、catch里面可以自己自定义，之后控制层调用服务层

/*获取经营单位数据*/
  public getUnitInfo() {
    this.parkManageService.getUnitInfo().then(data => {
      this.units = data.unit;
    });
  }

1.2 用Observable实现服务层

/*根据查询条件获取数据*/
  public getParkInfoByParams(jsonObject: any): Observable<any> {
    return this.http.request(this.getParkInfoByParamUrl, new RequestOptions({ method: 'GET', body: jsonObject }))
      .map((res: Response) => res.json())
      .catch((error: any) => Observable.throw(error || 'Server error'));
  }

控制层调用

 /*请求后台数据*/
  public getSuggests(pageNum: number) {
    this.suggestService.getSuggestInfo(`/Bi/${ConstantValue.CHECKCODE}/querySuggest/${pageNum}/${this.pageSize}`,
      this.getSearchParams())
      .subscribe(
        data => {
          // console.log(data);
          ...............
        },
        error => console.log('errorMsg:请求建议信息失败...')
      );
  }

 

2.Angular4 推出了一个新的http请求module：HttpClientModule

导入新的 HTTP Module

import {HttpClientModule} from '@angular/common/http';

@NgModule({
    declarations: [
        AppComponent
    ],
    imports: [
        BrowserModule,
        HttpClientModule
    ],
    providers: [],
    bootstrap: [AppComponent]
})
export class AppModule {}

需要注意的是，现在 JSON 是默认的数据格式，我们不需要再进行显式的解析。即我们不需要再使用以下代码：

http.get(url).map(res => res.json()).subscribe(...)

现在我们可以这样写：

http.get(url).subscribe(...)

发送get请求

public saveUser2() {
    let url = "http://localhost:8080/financial/user/getUsers/2";
    this.httpClient
    .get(url)
    .subscribe(data => {
      console.log(data)
    });
  }

带参数请求（REST方式请求不建议这样使用参数）

import {HttpParams} from "@angular/common/http";

const params = new HttpParams()
    .set('orderBy', '"$key"')
    .set('limitToFirst', "1");

this.courses$ = this.http
    .get("/courses.json", {params})9     .subscribe(data => _.values(data))

　　需要注意的是，我们通过链式语法调用 set() 方法，构建 HttpParams 对象。这是因为 HttpParams 对象是不可变的，通过 set() 方法可以防止该对象被修改。

每当调用 set() 方法，将会返回包含新值的 HttpParams 对象，因此如果使用下面的方式，将不能正确的设置参数。

const params = new HttpParams();
params.set('orderBy', '"$key"')
params.set('limitToFirst', "1");

使用 fromString 语法

const params = new HttpParams({fromString: 'orderBy="$key"&limitToFirst=1'});

使用 request() API

const params = new HttpParams({fromString: 'orderBy="$key"&limitToFirst=1'});

this.courses$ = this.http
    .request(
        "GET",
        "/courses.json", 
        {
            responseType:"json",
            params
        })
    .subscribe(data => _.values(data));

设置 HTTP Headers

const headers = new HttpHeaders().set("X-CustomHeader", "custom header value");

this.courses$ = this.http
    .get(
        "/courses.json",
        {headers})
    .subscribe(data => _.values(data));

发送 Put 请求

const headers = new HttpHeaders().set("Content-Type", "application/json");
 this.http.put("/courses/-KgVwECOnlc-LHb_B0cQ.json",
        {
            "courseListIcon": ".../main-page-logo-small-hat.png",
            "description": "Angular Tutorial For Beginners TEST",
            "iconUrl": ".../angular2-for-beginners.jpg",
            "longDescription": "...",
            "url": "new-value-for-url"
        },
        {headers})
        .subscribe(
            val => {
                console.log("PUT call successful value returned in body", val);
            },
            response => {
                console.log("PUT call in error", response);
            },
            () => {
                console.log("The PUT observable is now completed.");
            }
        );
}

发送 Patch 请求

httpPatchExample() {
    this.http.patch("/courses/-KgVwECOnlc-LHb_B0cQ.json",
        {
            "description": "Angular Tutorial For Beginners PATCH TEST",
        })
        .subscribe(
            (val) => {
                console.log("PATCH call successful value returned in body", 
                  val);
            },
            response => {
                console.log("PATCH call in error", response);
            },
            () => {
                console.log("The PATCH observable is now completed.");
            });
}

发送 Delete 请求

httpDeleteExample() {
    this.http.delete("/courses/-KgVwECOnlc-LHb_B0cQ.json")
        .subscribe(
            (val) => {
                console.log("DELETE call successful value returned in body",  val);
            },
            response => {
                console.log("DELETE call in error", response);
            },
            () => {
                console.log("The DELETE observable is now completed.");
            });
}

发送 Post 请求

httpPostExample() {
    this.http.post("/courses/-KgVwECOnlc-LHb_B0cQ.json",
        {
            "courseListIcon": "...",
            "description": "TEST",
            "iconUrl": "..",
            "longDescription": "...",
            "url": "new-url"
        })
        .subscribe(
            (val) => {
                console.log("POST call successful value returned in body",  val);
            },
            response => {
                console.log("POST call in error", response);
            },
            () => {
                console.log("The POST observable is now completed.");
            });
}

避免重复请求

duplicateRequestsExample() {
    const httpGet$ = this.http
        .get("/courses.json")
        .map(data => _.values(data));

    httpGet$.subscribe(
        (val) => console.log("logging GET value", val)
    );
    this.courses$ = httpGet$;
}

　　在上面例子中，我们正在创建了一个 HTTP observable 对象 httpGet$，接着我们直接订阅该对象。然后，我们把 httpGet$ 对象赋值给 courses$ 成员变量，最后在模板中使用 async 管道订阅该对象。这将导致发送两个 HTTP 请求，在这种情况下，请求显然是重复的，因为我们只希望从后端查询一次数据。为了避免发送冗余的请求，我们可以使用 RxJS 提供的 shareReplay 操作符：

// put this next to the other RxJs operator imports
import 'rxjs/add/operator/shareReplay';

const httpGet$ = this.http
    .get("/courses.json")
    .map(data => _.values(data))
    .shareReplay();

并行发送多个请求

并行发送 HTTP 请求的一种方法是使用 RxJs 中的 forkjoin 操作符：

import 'rxjs/add/observable/forkJoin';

parallelRequests() {

    const parallel$ = Observable.forkJoin(
        this.http.get('/courses/-KgVwEBq5wbFnjj7O8Fp.json'),
        this.http.get('/courses/-KgVwECOnlc-LHb_B0cQ.json')
    );

    parallel$.subscribe(
        values => {
            console.log("all values", values)
        }
    );
}

顺序发送 Http 请求

sequentialRequests() {
    const sequence$ = this.http.get<Course>('/courses/-KgVwEBq5wbFnjj7O8Fp.json')
        .switchMap(course => {
            course.description+= ' - TEST ';
            return this.http.put('/courses/-KgVwEBq5wbFnjj7O8Fp.json', course)
        });
        
    sequence$.subscribe();
}

获取顺序发送 Http 请求的结果

sequentialRequests() {
    const sequence$ = this.http.get<Course>('/courses/-KgVwEBq5wbFnjj7O8Fp.json')
        .switchMap(course => {
            course.description+= ' - TEST ';
            return this.http.put('/courses/-KgVwEBq5wbFnjj7O8Fp.json', course)
        },
         (firstHTTPResult, secondHTTPResult)  => [firstHTTPResult, secondHTTPResult]);

    sequence$.subscribe(values => console.log("result observable ", values) );
}

请求异常处理

throwError() {
    this.http
        .get("/api/simulate-error")
        .catch( error => {
            // here we can show an error message to the user,
            // for example via a service
            console.error("error catched", error);

            return Observable.of({description: "Error Value Emitted"});
        })
        .subscribe(
            val => console.log('Value emitted successfully', val),
            error => {
                console.error("This line is never called ",error);
            },
            () => console.log("HTTP Observable completed...")
        );
}

当发生异常时，控制台的输出结果：

Error catched 

HttpErrorResponse {headers: HttpHeaders, status: 404, statusText: "Not Found", url: "http://localhost:4200/api/simulate-error", ok: false, … }

Value emitted successfully {description: "Error Value Emitted"}
HTTP Observable completed...

Http 拦截器

定义拦截器

import {Injectable} from "@angular/core";
import {HttpEvent, HttpHandler, HttpInterceptor} from "@angular/common/http";
import {HttpRequest} from "@angular/common/http";
import {Observable} from "rxjs/Observable";

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
    
    constructor(private authService: AuthService) {
    }

    intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        const clonedRequest = req.clone({
            headers: req.headers.set('X-CustomAuthHeader', authService.getToken())
        });
        console.log("new headers", clonedRequest.headers.keys());
        return next.handle(clonedRequest);
    }
}

配置拦截器

@NgModule({
    declarations: [
        AppComponent
    ],
    imports: [
        BrowserModule,
        HttpClientModule
    ],
    providers: [
        [ { provide: HTTP_INTERCEPTORS, useClass: AuthInterceptor, multi: true } ]
    ],
    bootstrap: [AppComponent]
})
export class AppModule { }

Http 进度事件

longRequest() {
    const request = new HttpRequest(
        "POST", "/api/test-request", {}, 
         {reportProgress: true});

    this.http.request(request)
        .subscribe(
            event => {
                if (event.type === HttpEventType.DownloadProgress) {
                    console.log("Download progress event", event);
                }
                if (event.type === HttpEventType.UploadProgress) {
                    console.log("Upload progress event", event);
                }
                if (event.type === HttpEventType.Response) {
                    console.log("response received...", event.body);
                }
            }
        );
}

上面示例运行后，控制台的可能的输出结果：

Upload progress event Object {type: 1, loaded: 2, total: 2}
Download progress event Object {type: 3, loaded: 31, total: 31}
Response Received... Object {description: "POST Response"}