演示实例：AServlet发送一个Student对象到BServlet
#### 1.AServlet部分
首先造一个学生stu，然后通过fastjson的`toJSONString`方法把对象转换成字符串，再通过MyHttpUtils的`sendPost`方法把数据发送到BServlet
核心部分是`MyHttpUtils`类，还用到了`fastjson.jar`包
```java
@WebServlet("/AServet")
public class AServet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
Stu stu = new Stu();
stu.setAge(12);
stu.setName("ergou");
stu.setSex(1);
String str = JSON.toJSONString(stu);//将java对象转换为json字符串
response.getWriter().append("将发送请求给B");
String ret = MyHttpUtils.sendPost("http://localhost:8080/HttpServletTest/BServet", "data="+str);
System.out.println("来自BServlet的返回值：" + ret);
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
```
##### MyHttpUtils类
```java
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.URL;
import java.net.URLConnection;
public class MyHttpUtils {
/**
* 向指定 URL 发送POST方法的请求
*
* @param url
* 发送请求的 URL
* @param param
* 请求参数，请求参数应该是 name1=value1&name2=value2 的形式。
* @return 所代表远程资源的响应结果
*/
public static String sendPost(String url, String param) {
PrintWriter out = null;
BufferedReader in = null;
String result = "";
try {
URL realUrl = new URL(url);
// 打开和URL之间的连接
URLConnection conn = realUrl.openConnection();
// 设置通用的请求属性
conn.setRequestProperty("accept", "*/*");
conn.setRequestProperty("connection", "Keep-Alive");
conn.setRequestProperty("user-agent",
"Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
// 发送POST请求必须设置如下两行
conn.setDoOutput(true);
conn.setDoInput(true);
// 获取URLConnection对象对应的输出流
out = new PrintWriter(conn.getOutputStream());
// 发送请求参数
out.print(param);
// flush输出流的缓冲
out.flush();
// 定义BufferedReader输入流来读取URL的响应
in = new BufferedReader(
new InputStreamReader(conn.getInputStream()));
String line;
while ((line = in.readLine()) != null) {
result += line;
}
} catch (Exception e) {
System.out.println("发送 POST 请求出现异常！"+e);
e.printStackTrace();
}
//使用finally块来关闭输出流、输入流
finally{
try{
if(out!=null){
out.close();
}
if(in!=null){
in.close();
}
}
catch(IOException ex){
ex.printStackTrace();
}
}
return result;
}
}
```
#### 2.BServlet部分
接收来自AServlet的数据String，然后通过fastjson包的parseObject方法把字符串转成Stu对象，再取出需要的值
```java
/**
* Servlet implementation class AServet
*/
@WebServlet("/BServet")
public class BServet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
String data = request.getParameter("data");
if(data == null) {
response.getWriter().append("data为空");
return;
}
Stu stu = JSON.parseObject(data, Stu.class);
System.out.println();
System.out.println("收到请求，学生是: " + stu.getName());
response.getWriter().append("收到请求，学生是: " + stu.getName());
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
}
```
