ym——Android从零开始(16)(HTTP协议请求、获取图片、json数据)(新)
转载请注明本文出自Cym的博客（http://blog.csdn.net/cym492224103），谢谢支持！
前言
android应用开发必不可少的http协议通讯技术！
HTTP协议提交数据
搭建服务器环境
当下最流行的开发环境：
Eclipse
当下最流行的J2EE框架集成体系：
2.1 Struts2，MVC
2.2 Hibernate3，ORM
3.3 Spring Framework，IoC、AOP
get请求的参数是带在url后面
post的参数是以请求实体的形式
get请求是不安全的，以为可以被别人看见而且服务器对url的长度做了限制，
2k 4k 如果url过长，url就会被截取，
这样会导致数据的异常，post是安全。
// 1 创建路径
// 2 通过路径拿到连接
// 3 设置请求方式
// 4 设置超时时间
// 5 判断是否连接成功 n
// path 例： http://10.0.2.2:8081/xxxx/xxxx
StringBuilder sb = new StringBuilder(path);
// 拼接参数 例： ？Name=xxx&age =xxx
if(!params.isEmpty()){
sb.append("?");
for (Map.Entry<String, String> entry : params.entrySet()) {
String key = entry.getKey();
String value = entry.getValue();
sb.append(key).append("=").append(value);
sb.append("&");
}
}
sb.deleteCharAt(sb.length() - 1);
try {
URL url = new URL(sb.toString());
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
// 设置请求方式里面的参数一定要全大写
conn.setRequestMethod("GET");
conn.setReadTimeout(5000);
if (conn.getResponseCode() == HttpURLConnection.HTTP_OK) {
// -对web的反馈数据进行处理
InputStream is = conn.getInputStream();
ByteArrayOutputStream bos = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = 0;
while((len = is.read(buffer))!=-1)
{
bos.write(buffer, 0, len);
}
String data = bos.toString();
flag = data.equals("success")?true:false;
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Post
// post不需要在路径后面拼接参数
StringBuilder sb = new StringBuilder();
if(!params.isEmpty()){
for (Map.Entry<String, String> entry : params.entrySet()) {
String key = entry.getKey();
String value = entry.getValue();
sb.append(key).append("=").append(value);
sb.append("&");
}
}
sb.deleteCharAt(sb.length() - 1);
byte[] entity = sb.toString().getBytes();
try {
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("POST");
conn.setReadTimeout(5000);
//Content-Type: application/x-www-form-urlencoded
//Content-Length: 24
// 除了设置请求类型和请求超时时长外，一定要设置内容类型和内容长度
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
conn.setRequestProperty("Content-Length", entity.length+"");
// 设置允许输出
// 输出请求实体 例 name=xxx&age=xx
conn.setDoOutput(true);
OutputStream os = conn.getOutputStream();
os.write(entity);
if (conn.getResponseCode() == HttpURLConnection.HTTP_OK) {
InputStream is = conn.getInputStream();
ByteArrayOutputStream bos = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = 0;
while((len = is.read(buffer))!=-1)
{
bos.write(buffer, 0, len);
}
String data = bos.toString();
flag = data.equals("success")?true:false;
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
HttpClient
// 我们可以把它看作一个浏览器
特点：
1.需要引入第三方jar包(android内部提供)
2.基于HttpURLConnection的封装
3.能够满足复杂的需求（Cookit、Session）
4.基本操作简单
流程
1 拿到httpClient对象
2 创建请求方式对象(需要访问路径) httpGet（）
3 httpClient对象使用execute执行请求对象
4 得到返回对象，从返回对象上拿到返回码
5 对返回码进行判断
6 从返回对象上拿到返回值
StringBuilder sb = new StringBuilder(path);
if(!params.isEmpty()){
sb.append("?");
for (Map.Entry<String, String> entry : params.entrySet()) {
String key = entry.getKey();
String value = entry.getValue();
sb.append(key).append("=").append(value);
sb.append("&");
}
sb.deleteCharAt(sb.length() - 1);
}
// 可以看作浏览器
HttpClient httpClient = new DefaultHttpClient();
HttpGet request = new HttpGet(sb.toString());
// 执行请求
try {
HttpResponse response = httpClient.execute(request);
StatusLine line = response.getStatusLine();
int statueCode = line.getStatusCode();
if(statueCode == HttpStatus.SC_OK)｛
HttpEntity entity = response.getEntity();
InputStream is = entity.getContent();
ByteArrayOutputStream bos = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = 0;
while((len = is.read(buffer))!=-1)
{
bos.write(buffer, 0, len);
}
String data = bos.toString();
flag = data.equals("success")?true:false;
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Post
HttpClient httpClient = new DefaultHttpClient();
HttpPost request = new HttpPost(path);
// 执行请求
// 请求实体 NameValuePair
List<NameValuePair> parameters = new ArrayList<NameValuePair>();
for(Map.Entry<String, String> entry:params.entrySet())
{
String name = entry.getKey();
String value = entry.getValue();
NameValuePair nvp = new BasicNameValuePair(name, value);
parameters.add(nvp);
}
UrlEncodedFormEntity uefe = new UrlEncodedFormEntity(parameters);
// 发送请求实体
request.setEntity(uefe);
HttpResponse response = httpClient.execute(request);
StatusLine line = response.getStatusLine();
int statueCode = line.getStatusCode();
if(statueCode == HttpStatus.SC_OK)
{
HttpEntity entity = response.getEntity();
InputStream is = entity.getContent();
ByteArrayOutputStream bos = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = 0;
while((len = is.read(buffer))!=-1)
{
bos.write(buffer, 0, len);
}
String data = bos.toString();
获取图片
ImageView img = (ImageView) findViewById(R.id.iv);
URL url;
try {
url = new URL("http://10.0.2.2:8081/myssh/login.png");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("GET");
conn.setReadTimeout(2000);
if(conn.getResponseCode() == 200)
{
InputStream is = conn.getInputStream();
img.setImageBitmap(BitmapFactory.decodeStream(is));
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
xml
// 拿到连接对象使用pull解析读取
Json
// 拿到连接对象读取完json格式的字符串
使用JSONArray解析
String json = bos.toString();
JSONArray jsonArray = new JSONArray(json);
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject object = jsonArray.getJSONObject(i);
list.add(new Users(object.getInt("id"), object.getString("name"), object.getString("pwd")));
}