JSON实现Android 网络数据交换（包括复杂对象的传送）
1，服务端到客户端
服务端新建Json数据，HttpservletResponse是请求对象的返回，得到他的writer，把json转换成string就可以。写在doGet里。
代码：

res.setContentType("UTF-8");
PrintWriter pw = res.getWriter();
JSONObject json = new JSONObject();
json.put("name","fwz");
pw.write(json.toString());

客户端，使用HttpClient的execute的方法。用httpGet去执行。返回HttpResponse。再从response读取。
代码：

BufferedReader  bufferedReader = null;
        StringBuilder sb = new StringBuilder();
        String s = "";
        try {
HttpClient client = new DefaultHttpClient();
HttpResponse response = client.execute(new HttpGet("http://10.0.2.2:8080/myFirstServlet/JSONServer"));
HttpParams httpParams = client.getParams();
HttpConnectionParams.setConnectionTimeout(httpParams, 3000);
HttpConnectionParams.setSoTimeout(httpParams, 5000);
HttpEntity entity = response.getEntity();
if (entity!=null) {
bufferedReader = new BufferedReader(new InputStreamReader(entity.getContent(),"UTF-8"));  //8192
while((s=bufferedReader.readLine())!=null) {
sb.append(s);   
}
}
nameTextView.setText(sb.toString());  //这里输出得到的JSon数据（未解析）
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}

2，客户端到服务器端的传送

客户端，跟前面差不多，也是利用httpClient的execute方法，不过发送数据用Post。结合entity。
代码：

HttpClient client = new DefaultHttpClient();
HttpPost post = new HttpPost("http://10.0.2.2:8080/myFirstServlet/JSONServer");
JSONObject jsonObject = new JSONObject();
try {
jsonObject.put("name", "ze");
StringEntity entity = new StringEntity(jsonObject.toString());
post.setEntity(entity);
HttpResponse responString = client.execute(post);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

服务端，只要写一个读取的方法就可以，在方法里处理HttpservletRequest的数据
代码：  这里只是输出

try {
BufferedInputStream in = new BufferedInputStream(req.getInputStream());
    int i;
    char c;
    while ((i=in.read())!=-1) {
    c=(char)i;
    System.out.print(c);
    }
    System.out.println();
    System.out.println("test");
}
catch (Exception ex) {
ex.printStackTrace();
}