使用JAVA实现http通信详解
http通信概述
http通信主要有两种方式post方式和get方式。前者通过http消息实体发送数据给服务器,安全性高,数据传输大小没有限制,后者通过url的查询字符串传递给服务器参数,以明文显示在浏览器地址栏,保密性差,最多传输2048个字符。但是get请求并不是一无是处——get请求大多用于查询(读取资源),效率高。post请求用于注册、登录等安全性较高且向数据库中写入数据的操作。
除了post和get,http通信还有其他方式!请参见http请求的方法
编码前的准备
在进行编码之前,我们先创建一个servlet,该servlet接收客户端的参数(name和age),并响应客户端。
@webservlet(urlpatterns={"/demo.do"}) public class demoservlet extends httpservlet { private static final long serialversionuid = 1l; public void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception { request.setcharacterencoding("utf-8"); response.setcontenttype("text/html;charset=utf-8"); string name = request.getparameter("name"); string age = request.getparameter("age"); printwriter pw = response.getwriter(); pw.print("您使用get方式请求该servlet。<br />" + "name = " + name + ",age = " + age); pw.flush(); pw.close(); } public void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception { request.setcharacterencoding("utf-8"); response.setcontenttype("text/html;charset=utf-8"); string name = request.getparameter("name"); string age = request.getparameter("age"); printwriter pw = response.getwriter(); pw.print("您使用post方式请求该servlet。<br />" + "name = " + name + ",age = " + age); pw.flush(); pw.close(); } }
使用jdk实现http通信
使用urlconnection实现get请求
实例化一个java.net.url对象;
通过url对象的openconnection()方法得到一个java.net.urlconnection;
通过urlconnection对象的getinputstream()方法获得输入流;
读取输入流;
关闭资源。
public void get() throws exception{ url url = new url("http://127.0.0.1/http/demo.do?name=jack&age=10"); urlconnection urlconnection = url.openconnection(); // 打开连接 bufferedreader br = new bufferedreader(new inputstreamreader(urlconnection.getinputstream(),"utf-8")); // 获取输入流 string line = null; stringbuilder sb = new stringbuilder(); while ((line = br.readline()) != null) { sb.append(line + "\n"); } system.out.println(sb.tostring()); }
使用httpurlconnection实现post请求
java.net.httpurlconnection是java.net.url的子类,提供了更多的关于http的操作(getxxx 和 setxxx方法)。该类中定义了一系列的http状态码:
public void post() throws ioexception{ url url = new url("http://127.0.0.1/http/demo.do"); httpurlconnection httpurlconnection = (httpurlconnection) url.openconnection(); httpurlconnection.setdoinput(true); httpurlconnection.setdooutput(true); // 设置该连接是可以输出的 httpurlconnection.setrequestmethod("post"); // 设置请求方式 httpurlconnection.setrequestproperty("charset", "utf-8"); printwriter pw = new printwriter(new bufferedoutputstream(httpurlconnection.getoutputstream())); pw.write("name=welcome"); // 向连接中输出数据(相当于发送数据给服务器) pw.write("&age=14"); pw.flush(); pw.close(); bufferedreader br = new bufferedreader(new inputstreamreader(httpurlconnection.getinputstream(),"utf-8")); string line = null; stringbuilder sb = new stringbuilder(); while ((line = br.readline()) != null) { // 读取数据 sb.append(line + "\n"); } system.out.println(sb.tostring()); }
使用httpclient进行http通信
httpclient大大简化了jdk中http通信的实现。
maven依赖:
<dependency> <groupid>org.apache.httpcomponents</groupid> <artifactid>httpclient</artifactid> <version>4.3.6</version> </dependency>
get请求
public void httpclientget() throws exception{ // 创建httpclient对象 httpclient client = httpclients.createdefault(); // 创建get请求(在构造器中传入url字符串即可) httpget get = new httpget("http://127.0.0.1/http/demo.do?name=admin&age=40"); // 调用httpclient对象的execute方法获得响应 httpresponse response = client.execute(get); // 调用httpresponse对象的getentity方法得到响应实体 httpentity httpentity = response.getentity(); // 使用entityutils工具类得到响应的字符串表示 string result = entityutils.tostring(httpentity,"utf-8"); system.out.println(result); }
post请求
public void httpclientpost() throws exception{ // 创建httpclient对象 httpclient client = httpclients.createdefault(); // 创建post请求 httppost post = new httppost("http://127.0.0.1/http/demo.do"); // 创建一个list容器,用于存放基本键值对(基本键值对即:参数名-参数值) list<basicnamevaluepair> parameters = new arraylist<>(); parameters.add(new basicnamevaluepair("name", "张三")); parameters.add(new basicnamevaluepair("age", "25")); // 向post请求中添加消息实体 post.setentity(new urlencodedformentity(parameters, "utf-8")); // 得到响应并转化成字符串 httpresponse response = client.execute(post); httpentity httpentity = response.getentity(); string result = entityutils.tostring(httpentity,"utf-8"); system.out.println(result); }
httpclient是apache jakarta common下的子项目,用来提供高效的、最新的、功能丰富的支持http协议的客户端编程工具包,并且它支持http协议最新的版本和建议。httpclient已经应用在很多的项目中,比如apache jakarta上很著名的另外两个开源项目cactus和htmlunit都使用了httpclient。