什么是httpclient
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。实现了所有 HTTP 的方法（GET,POST,PUT,HEAD 等）
httpclient作用
在java代码中，发送Http请求。通常用来实现远程接口调用。
说明：在ego-base中测试
在ego-base工程中添加httpclient的pom依赖。
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
</dependency>
执行GET请求
public static void doGet(){
//创建Httpclient对象
CloseableHttpClient httpclient = HttpClients.createDefault();
//创建httpGET请求
HttpGet httpGet = new HttpGet("http://www.oschina.net/");
CloseableHttpResponse response = null;
try {
//执行请求
response = httpclient.execute(httpGet);
System.out.println(response.getStatusLine());
//判断返回状态是否为200
if (response.getStatusLine().getStatusCode() == 200) {
String content = EntityUtils.toString(response.getEntity(), "UTF-8");
System.out.println("内容长度：" + content.length());
}
}catch(Exception e){
e.printStackTrace();
} finally {
if (response != null) {
try {
response.close();
} catch (IOException e) {
e.printStackTrace();
}
}
try {
httpclient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
执行GET带参数
public static void doGetParam(){
//创建Httpclient对象
CloseableHttpClient httpclient = HttpClients.createDefault();
CloseableHttpResponse response = null;
try {
//定义请求的参数
URI uri = new URIBuilder("http://www.baidu.com/s").setParameter("wd", "数据库").build();
System.out.println(uri);
//创建http GET请求
HttpGet httpGet = new HttpGet(uri);
//执行请求
response = httpclient.execute(httpGet);
//判断返回状态是否为200
if (response.getStatusLine().getStatusCode() == 200) {
String content = EntityUtils.toString(response.getEntity(), "UTF-8");
System.out.println(content);
}
}catch(Exception e){
e.printStackTrace();
}finally {
if (response != null) {
try {
response.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
try {
httpclient.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
执行post请求
public static void doPost(){
//创建Httpclient对象
CloseableHttpClient httpclient = HttpClientBuilder.create().setRedirectStrategy(new LaxRedirectStrategy()).build();
//创建httpPOST请求
HttpPost httpPost = new HttpPost("http://www.oschina.net/");
CloseableHttpResponse response = null;
try {
//执行请求
response = httpclient.execute(httpPost);
System.out.println(response.getStatusLine());
//判断返回状态是否为200
if (response.getStatusLine().getStatusCode() == 200) {
String content = EntityUtils.toString(response.getEntity(), "UTF-8");
System.out.println(content);
}
}catch(Exception e){
e.printStackTrace();
}finally {
if (response != null) {
try {
response.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
try {
httpclient.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
执行post带参数
public static void doPostParam() throws Exception{
//创建Httpclient对象
CloseableHttpClient httpclient = HttpClientBuilder.create().setRedirectStrategy(new LaxRedirectStrategy()).build();
//创建httpPOST请求
HttpPost httpPost = new HttpPost("http://www.oschina.net/search");
//设置2个post参数，一个是scope、一个是q
List<NameValuePair> parameters = new ArrayList<NameValuePair>();
parameters.add(new BasicNameValuePair("scope", "project"));
parameters.add(new BasicNameValuePair("q", "java"));
//构造一个form表单式的实体
UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(parameters);
//将请求实体设置到httpPost对象中
httpPost.setEntity(formEntity);
CloseableHttpResponse response = null;
try {
//执行请求
response = httpclient.execute(httpPost);
System.out.println(response.getStatusLine());
//判断返回状态是否为200
if (response.getStatusLine().getStatusCode() == 200) {
String content = EntityUtils.toString(response.getEntity(), "UTF-8");
System.out.println(content);
}
} finally {
if (response != null) {
response.close();
}
httpclient.close();
}
}
请求参数乱码
设置请求的编码格式：
obj.addHeader("Content-Type","application/x-www-form-urlencoded; charset=UTF-8");
响应HTTP/1.1 403 Forbidden
原因：网站设置了反爬虫机制，禁止非法访问。
解决方案：伪装浏览器。
obj.addHeader("User-Agent"," Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537. 36 (KHTML, like Gecko) Chrome/31.0.1650.63")
public class HttpClientUtils {
public static String doGet(String url,Map<String, String> params){
//获取httpclient客户端
CloseableHttpClient httpclient = HttpClients.createDefault();
String resultString = "";
CloseableHttpResponse response = null;
try {
URIBuilder builder = new URIBuilder(url);
if(null!=params){
for (String key:params.keySet()) {
builder.setParameter(key, params.get(key));
}
}
HttpGet get = new HttpGet(builder.build());
response = httpclient.execute(get);
System.out.println(response.getStatusLine());
if(200==response.getStatusLine().getStatusCode()){
HttpEntity entity = response.getEntity();
resultString = EntityUtils.toString(entity, "utf-8");
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if(null!=response){
try {
response.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(null!=httpclient){
try {
httpclient.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
return resultString;
}
public static String doGet(String url){
return doGet(url, null);
}
public static String doPost(String url,Map<String,String> params){
/**
*在4.0及以上httpclient版本中，post需要指定重定向的策略，如果不指定则按默认的重定向策略。
*
*获取httpclient客户端
*/
CloseableHttpClient httpclient = HttpClientBuilder.create().setRedirectStrategy( new LaxRedirectStrategy()).build();
String resultString = "";
CloseableHttpResponse response = null;
try {
HttpPost post = new HttpPost(url);
List<NameValuePair> paramaters = new ArrayList<>();
if(null!=params){
for (String key : params.keySet()) {
paramaters.add(new BasicNameValuePair(key,params.get(key)));
}
UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity (paramaters);
post.setEntity(formEntity);
}
/**
* HTTP/1.1 403 Forbidden
*原因：
*有些网站，设置了反爬虫机制
*解决的办法：
*设置请求头，伪装浏览器
*/
post.addHeader("user-agent", "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36");
response = httpclient.execute(post);
System.out.println(response.getStatusLine());
if(200==response.getStatusLine().getStatusCode()){
HttpEntity entity = response.getEntity();
resultString = EntityUtils.toString(entity, "utf-8");
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if(null!=response){
try {
response.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(null!=httpclient){
try {
httpclient.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
return resultString;
}
public static String doPost(String url){
return doPost(url, null);
}
}
