跨域请求httpclient

httpclient：是Apache工具包，util，它可以作为一个爬虫，直接爬取某个互联网上的页面。获取到时页面最终的源文件html。直接可以获取页面返回json。就可以直接在代码内部模拟发起http请求。请求的结果也被捕捉。在代码内部将获取的json，利用JacksonObjectMapper对象，把json字符串转成java对象。

与Spring框架整合：

1、引入jar支持

<!-- httpclient -->
<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.3.5</version>
</dependency>
<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpmime</artifactId>
    <version>4.3.1</version>
</dependency>

2、applicationContext-httpclient.xml：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:p="http://www.springframework.org/schema/p"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
    http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
    http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.0.xsd">

    <!-- 定义httpclient连接池 -->
    <bean id="httpClientConnectionManager" class="org.apache.http.impl.conn.PoolingHttpClientConnectionManager" destroy-method="close">
        <!-- 设置连接总数 -->
        <property name="maxTotal" value="${http.pool.maxTotal}"></property>
        <!-- 设置每个地址的并发数 -->
        <property name="defaultMaxPerRoute" value="${http.pool.defaultMaxPerRoute}"></property>
    </bean>

    <!-- 定义 HttpClient工厂，这里使用HttpClientBuilder构建-->
    <bean id="httpClientBuilder" class="org.apache.http.impl.client.HttpClientBuilder" factory-method="create">
        <property name="connectionManager" ref="httpClientConnectionManager"></property>
    </bean>

    <!-- 得到httpClient的实例 -->
    <bean id="httpClient" factory-bean="httpClientBuilder" factory-method="build"/>

    <!-- 定期清理无效的连接 -->
    <bean class="com.jt.common.util.IdleConnectionEvictor" destroy-method="shutdown">
        <constructor-arg index="0" ref="httpClientConnectionManager" />
        <!-- 间隔一分钟清理一次 -->
        <constructor-arg index="1" value="600000" />
    </bean>

    <!-- 定义requestConfig的工厂 -->
    <bean id="requestConfigBuilder" class="org.apache.http.client.config.RequestConfig.Builder">
        <!-- 从连接池中获取到连接的最长时间 -->
        <property name="connectionRequestTimeout" value="${http.request.connectionRequestTimeout}"/>
        <!-- 创建连接的最长时间 -->
        <property name="connectTimeout" value="${http.request.connectTimeout}"/>
        <!-- 数据传输的最长时间 -->
        <property name="socketTimeout" value="${http.request.socketTimeout}"/>
        <!-- 提交请求前测试连接是否可用 -->
        <property name="staleConnectionCheckEnabled" value="${http.request.staleConnectionCheckEnabled}"/>
    </bean>    

    <!-- 得到requestConfig实例 -->
    <bean id="requestConfig" factory-bean="requestConfigBuilder" factory-method="build" />

</beans>

3、把httpClient对象封装成伪service。在程序中注入，封装doGet,doPost,doJson-    ---- HttpClientService：

package com.jt.common.service;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import org.apache.http.NameValuePair;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class HttpClientService {

    private static final Logger LOGGER = LoggerFactory.getLogger(HttpClientService.class);

    @Autowired(required=false)
    private CloseableHttpClient httpClient;

    @Autowired(required=false)
    private RequestConfig requestConfig;

    /**
     * 执行get请求
     *
     * @param url
     * @return
     * @throws Exception
     */
    public String doGet(String url,Map<String, String> params,String encode) throws Exception {
        LOGGER.info("执行GET请求，URL = {}", url);
        if(null != params){
            URIBuilder builder = new URIBuilder(url);
            for (Map.Entry<String, String> entry : params.entrySet()) {
                builder.setParameter(entry.getKey(), entry.getValue());
            }
            url = builder.build().toString();
        }
        // 创建http GET请求
        HttpGet httpGet = new HttpGet(url);
        httpGet.setConfig(requestConfig);
        CloseableHttpResponse response = null;
        try {
            // 执行请求
            response = httpClient.execute(httpGet);
            // 判断返回状态是否为200
            if (response.getStatusLine().getStatusCode() == 200) {
                if(encode == null){
                    encode = "UTF-8";
                }
                return EntityUtils.toString(response.getEntity(), encode);
            }
        } finally {
            if (response != null) {
                response.close();
            }
            // 此处不能关闭httpClient，如果关闭httpClient，连接池也会销毁
        }
        return null;
    }

    public String doGet(String url, String encode) throws Exception{
        return this.doGet(url, null, encode);
    }

    public String doGet(String url) throws Exception{
        return this.doGet(url, null, null);
    }

    /**
     * 带参数的get请求
     *
     * @param url
     * @param params
     * @return
     * @throws Exception
     */
    public String doGet(String url, Map<String, String> params) throws Exception {
        return this.doGet(url, params, null);
    }

    /**
     * 执行POST请求
     *
     * @param url
     * @param params
     * @return
     * @throws Exception
     */
    public String doPost(String url, Map<String, String> params,String encode) throws Exception {
        // 创建http POST请求
        HttpPost httpPost = new HttpPost(url);
        httpPost.setConfig(requestConfig);

        if (null != params) {
            // 设置2个post参数，一个是scope、一个是q
            List<NameValuePair> parameters = new ArrayList<NameValuePair>(0);
            for (Map.Entry<String, String> entry : params.entrySet()) {
                parameters.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));
            }

            // 构造一个form表单式的实体
            UrlEncodedFormEntity formEntity = null;
            if(encode!=null){
                formEntity = new UrlEncodedFormEntity(parameters,encode);
            }else{
                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);
            // 判断返回状态是否为200
            if (response.getStatusLine().getStatusCode() == 200) {
                return EntityUtils.toString(response.getEntity(), "UTF-8");
            }
        } finally {
            if (response != null) {
                response.close();
            }
        }
        return null;
    }

    /**
     * 执行POST请求
     *
     * @param url
     * @param params
     * @return
     * @throws Exception
     */
    public String doPost(String url, Map<String, String> params) throws Exception {
        // 创建http POST请求
        HttpPost httpPost = new HttpPost(url);
        httpPost.setConfig(requestConfig);

        if (null != params) {
            // 设置2个post参数，一个是scope、一个是q
            List<NameValuePair> parameters = new ArrayList<NameValuePair>(0);
            for (Map.Entry<String, String> entry : params.entrySet()) {
                parameters.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));
            }

            // 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);
            // 判断返回状态是否为200
            if (response.getStatusLine().getStatusCode() == 200) {
                return EntityUtils.toString(response.getEntity(), "UTF-8");
            }
        } finally {
            if (response != null) {
                response.close();
            }
        }
        return null;
    }

    public String doPostJson(String url, String json) throws Exception {
        // 创建http POST请求
        HttpPost httpPost = new HttpPost(url);
        httpPost.setConfig(requestConfig);

        if(null != json){
            //设置请求体为 字符串
            StringEntity stringEntity = new StringEntity(json,"UTF-8");
            httpPost.setEntity(stringEntity);
        }

        CloseableHttpResponse response = null;
        try {
            // 执行请求
            response = httpClient.execute(httpPost);
            // 判断返回状态是否为200
            if (response.getStatusLine().getStatusCode() == 200) {
                return EntityUtils.toString(response.getEntity(), "UTF-8");
            }
        } finally {
            if (response != null) {
                response.close();
            }
        }
        return null;
    }

}

4、在程序中注入httpClientService，直接调用doGet。

5、在applicationContext.xml中加入<value>classpath:httpclient.properties</value>

　　httpclient.properties：

#从连接池中获取到连接的最长时间
http.request.connectionRequestTimeout=500
#5000
http.request.connectTimeout=5000
#数据传输的最长时间
http.request.socketTimeout=30000
#提交请求前测试连接是否可用
http.request.staleConnectionCheckEnabled=true

#设置连接总数
http.pool.maxTotal=200
#设置每个地址的并发数
http.pool.defaultMaxPerRoute=100