小编Leg*_*cks的帖子

我这里有组件代码，当我订阅可观察对象时，服务被调用两次，但是如果我订阅Behavioursubject，它只会触发一次，

我可以在我的日志中看到这些结果，请参阅下面我的组件代码，在 ngOninit 上调用 subscribeToMap() 方法。

import { Component, OnInit } from '@angular/core';
import { Router }            from '@angular/router';

import { Observable }        from 'rxjs/Observable';
import { Subject }           from 'rxjs/Subject';

// Observable class extensions
import 'rxjs/add/observable/of';

// Observable operators
import 'rxjs/add/operator/catch';
import 'rxjs/add/operator/debounceTime';
import 'rxjs/add/operator/distinctUntilChanged';

import { HeroSearchService } from './hero-search-service';
import { Hero } from './../hero';

@Component({
  selector: 'hero-search',
  templateUrl: './hero-search.component.html',
  styleUrls: [ './hero-search.component.css' ],
  providers: [HeroSearchService]
})
export class HeroSearchComponent implements OnInit {
  heroes: Observable<Hero[]>;
  private searchTerms …

什么时候调用ProcessRequest方法？

我很难为什么,为什么以及如何调用流程请求？调用它的原因以及servlet容器如何调用它.

我在Netbeans 7.2上遇到这个错误,它说ClassNotFoundexception和InstantationException.我真的被这个问题困住了.请帮助我.

protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    try {
        String driver = "com.mysql.jdbc.Driver";
        con = null;
        String username = "";
        String password = "";

        Class.forName("com.mysql.jdbc.Driver").newInstance();

        con = DriverManager.getConnection("jdbc:mysql://localhost:3306/dbName", "root", "password");
        Statement st = con.createStatement();
        ResultSet mar = st.executeQuery("SELECT * FROM table");


        Gson gson = new GsonBuilder().create();
        response.setContentType("application/json");  
        response.setCharacterEncoding("utf-8"); 

    } catch (SQLException e) {
                String message = e.getMessage();
    }

我正在编写一个servlet,它将接受来自AJAX请求的POST数据.

这是我从客户端发送的代码:

$.ajax({
            type: "POST",
            url: "urlservlet",
            data: "{type:'" + "country" + 
            "', country:'" + $('#country').val() +
            "'}",
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            success: function(response) {

            }

这是servlet代码:

protected void doPost(HttpServletRequest request, HttpServletResponse response)
                      throws ServletException, IOException {
    string test = request.getParameter("type");
}

但问题是我总是得到等于null的类型.我不知道为什么.

请帮助我.