使用Apache提供的HttpClient对象调用HTTP接口(基于POST请求)

本篇将主要介绍如何使用HttpClient4.5版本调用接口的实例.(实现代码中有大量注释供理解所用)

先准备好一个Springboot项目,方便自己编写接口与后台直接main方法调用.

Springboot工程结构展示:

准备好后,第一步引入Apache提供的HttpClient4.5版本的依赖包.

依赖如下:

<dependency>
    <groupId>org.apache.httpcomponents</groupId>
    <artifactId>httpclient</artifactId>
    <version>4.5.6</version>
</dependency>

引入好依赖包后,第二步我们先简单的在Controller层中编写基于POST方法的接口.

1.POST请求一般用于提交数据,所以先创建一个User实体类用于自动接收参数.(记得重写toString()方法,方便查看属性值)

public class User {

    private int id;
    private String username;
    private String password;

    public User(){

    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

 2.在Controller层,编写POST请求的接口

@ResponseBody
    @RequestMapping(value = "/user/save",method = {RequestMethod.POST})
    public String saveUserMsg(User user){
        //因重写了User的toString()方法,会直接输出属性值
        System.out.println(user);
        return "保存用户已执行...";
    }

由于此接口是基于POST方法的,所以无法在浏览器中测试.可以使用SoapUI或Postman等接口测试工具测试.

第三步,编写HttpClientUtil工具类,然后直接main方法调用POST接口即可.

/**
     * 使用HttpClient4.5版本对指定接口路径发送POST请求
     * @param httpUrl   指定接口路径
     * @param params    接口路径需要携带的参数集
     * @return  接口返回的消息
     */
    public static String doPost(String httpUrl,Map<String,Object> params){
        String result = null;
        //声明httpClient,httpResponse于try...catch语句外.方便最后关闭资源
        CloseableHttpClient httpClient = null;
        CloseableHttpResponse httpResponse = null;
        try{
            httpClient = HttpClients.createDefault();
            HttpPost httpPost = new HttpPost(httpUrl);
            //HttpEntity是一个接口,所有参数均是通过其子类携带
            //声明HttpEntity的实现子类UrlEncodedFormEntity用于携带参数
            //UrlEncodedFormEntity构造函数只接受BasicNameValuePair对象,符合程序逻辑
            UrlEncodedFormEntity formEntity = null;
            if(!params.isEmpty()){
                //获取Map集合的键集合
                Set<String> keySet = params.keySet();
                Iterator iterator = keySet.iterator();
                List<NameValuePair> list = new ArrayList<>();
                while (iterator.hasNext()){
                   String key = (String)iterator.next();
                   Object value = params.get(key);
                   //BasicNameValuePair通常是用来封装post请求中的参数名称和值
                   BasicNameValuePair basicNameValuePair = new BasicNameValuePair(key,value.toString());
                   list.add(basicNameValuePair);
                }
                //构造器方式注入Entity
                formEntity = new UrlEncodedFormEntity(list);
            }
            //将绑定了参数的HttpEntity子类实现类存入HttpPost对象中
            httpPost.setEntity(formEntity);
            //设置请求头
            httpPost.setHeader("Content-type","application/x-www-form-urlencoded");
            //向指定接口发送POST请求
            httpResponse = httpClient.execute(httpPost);
            if(httpResponse.getStatusLine().getStatusCode()==200){
                result = EntityUtils.toString(httpResponse.getEntity());
            }
        } catch(Exception e){
            e.printStackTrace();
        } finally {
            //逐一关闭使用过的资源
            try{
                if(httpResponse!=null){
                    httpResponse.close();
                }
                if(httpClient!=null){
                    httpClient.close();
                }
            }catch (Exception e){
                e.printStackTrace();
            }
        }
        return result;
    }

第四步,便可以在HttpClientUtil工具类main方法中调用doPost方法.访问POST接口.

public static void main(String[] args) {
        Map<String,Object> params = new HashMap<>();
        params.put("id",1);
        params.put("username","shanghai");
        params.put("password","000000");
        System.out.println(HttpClientUtil.doPost("http://127.0.0.1:8080/user/save",params));
    }

调用结果如下图:

main程序输出返回值如下:

Springboot接口输出结果如下:

以上便完成了使用HttpClient对象向接口发送POST请求的任务