我打电话给一个愚蠢的服务,回到查克诺里斯的笑话.这实际上工作正常.但是我收到的是Typescript控制台错误.

我在这里转载：
https://stackblitz.com/edit/angular-chuck

非常感谢您的期待.

data.service.ts

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';

import { DataModel } from './data.model';

@Injectable()
export class DataService {
  constructor( private http: HttpClient ) { }

  chuckUrl = 'https://api.chucknorris.io/jokes/random';

  getChuck() {
      return this.http.get<DataModel>(this.chuckUrl);
  }

}

data.model.ts

export class DataModel {
    public category: any;
    public icon_url: string;
    public id: string;
    public url: string;
    public value: string;
}

data.component

import { Component,OnInit } from '@angular/core';
import { DataService } from './data.service';
import { DataModel } from './data.model';

@Component({
    selector: 'app-data',templateUrl: './data.component.html'
})

export class AppData implements OnInit {
    constructor(private dataService: DataService) { }

    joke: DataModel;

    ngOnInit() {

        this.dataService.getChuck()
            .subscribe(
                (data: DataModel ) => {
                  if (data.category != 'explicit') {
                    this.joke = data;
                  } 
                }
            ); 
    }

}

<div>{{ joke?.value }}</div>

在API响应到达之前,您的笑话对象没有值.这样使用？应用空检查直到响应到达.

异常信息：

04-Aug-2014 15:49:27.894 SEVERE [http-apr-8080-exec-5] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [cms] in context with path [/cms] threw exception [Request processing failed; nested exception is org.springframework.validation.BindException: org.springframework.validation.BeanPropertyBindingResult: 6 errors Field error in object ''carContractSearchBox'' on field ''createEndDate'': rejected value []; codes [typeMismatch.carContractSearchBox.createEndDate,typeMismatch.createEndDate,typeMismatch.java.util.Date,typeMismatch]; arguments [org.springframework.context.support.DefaultMessageSourceResolvable: codes [carContractSearchBox.createEndDate,createEndDate]; arguments []; default message [createEndDate]]; default message [Failed to convert property value of type ''java.lang.String'' to required type ''java.util.Date'' for property ''createEndDate''; nested exception is java.lang.IllegalStateException: Cannot convert value of type [java.lang.String] to required type [java.util.Date] for property ''createEndDate'': no matching editors or conversion strategy found]

先说明一下，我们的项目使用的是 Spring MVC。相应的功能是一个简单的 form 表单查询功能，里面有一些日期字段的查询。

相应的解决办法为：

在对应的 controller 中增加属性编辑器：

@InitBinder
protected void initBinder(WebDataBinder binder) { SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd"); binder.registerCustomEditor(Date.class, new CustomDateEditor(dateFormat, true)); }

注意这块的 new CustomDateEditor(dateFormat, true) 中的 true，查看 CustomDateEditor 源码可以看到：

/**
 * Create a new CustomDateEditor instance, using the given DateFormat
 * for parsing and rendering.
 * <p>The "allowEmpty" parameter states if an empty String should
 * be allowed for parsing, i.e. get interpreted as null value.
 * Otherwise, an IllegalArgumentException gets thrown in that case.
 * @param dateFormat DateFormat to use for parsing and rendering
 * @param allowEmpty if empty strings should be allowed
 */
public CustomDateEditor(DateFormat dateFormat, boolean allowEmpty) { this.dateFormat = dateFormat; this.allowEmpty = allowEmpty; this.exactDateLength = -1; }

当 allowEmpty 字段为 true 的时候 form 表单传递的值可以为空。否则会出现 "" 字符串解析为 date 报错。