java中发送get请求

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1、创建get请求：

public static String doGet(String url, String charset)
            throws IOException {
        HttpURLConnection conn = null;
        String rsp = null;

        try {
            String ctype = "application/x-www-form-urlencoded;charset=" + charset;
            conn = getConnection(new URL(url), "GET", ctype);
            rsp = getResponseAsString(conn);
        } finally {
            if (conn != null) {
                conn.disconnect();
            }
        }

        return rsp;
    }

url为请求URL，charset为编码格式。

2、获取http连接

private static HttpURLConnection getConnection(URL url, String method, String ctype)
            throws IOException {
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestMethod(method);
        conn.setDoInput(true);
        conn.setDoOutput(true);
        conn.setRequestProperty("Accept", "text/xml,text/javascript,text/html,application/json");
        conn.setRequestProperty("Content-Type", ctype);
        conn.setConnectTimeout(5*60*1000);//连接超时
        conn.setReadTimeout(5*60*1000);//读取数据超时
        return conn;
    }

method定义为GET或POST。

3、获取响应（字符串形式）

private static String getResponseAsString(HttpURLConnection conn) throws IOException {
        String charset = getResponseCharset(conn.getContentType());
        InputStream es = conn.getErrorStream();
        if (es == null) {
            return getStreamAsString(conn.getInputStream(), charset);
        } else {
            String msg = getStreamAsString(es, charset);
            if (StringUtils.isEmpty(msg)) {
                throw new IOException(conn.getResponseCode() + ":" + conn.getResponseMessage());
            } else {
                throw new IOException(msg);
            }
        }
    }

4、获取响应的编码格式

private static String getResponseCharset(String ctype) {
        String charset = "UTF-8";
        if (!StringUtils.isEmpty(ctype)) {
            String[] params = ctype.split(";");
            for (String param : params) {
                param = param.trim();
                if (param.startsWith("charset")) {
                    String[] pair = param.split("=", 2);
                    if (pair.length == 2) {
                        if (!StringUtils.isEmpty(pair[1])) {
                            charset = pair[1].trim();
                        }
                    }
                    break;
                }
            }
        }
        return charset;
    }

5、通过输出流获取响应字符串

private static String getStreamAsString(InputStream stream, String charset) throws IOException {
        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(stream, charset));
            StringWriter writer = new StringWriter();
            char[] chars = new char[1024];
            int count = 0;
            while ((count = reader.read(chars)) > 0) {
                writer.write(chars, 0, count);
            }
            return writer.toString();
        } finally {
            if (stream != null) {
                stream.close();
            }
        }
    }