Exception in thread "main" java.lang.IllegalArgumentException: Illegal character in query at index x

HttpClient:

超文本传输​​协议（HTTP）可能是当今互联网上使用的最重要的协议。Web服务，启用网络的设备和网络计算的增长继续扩展了HTTP协议在用户驱动的Web浏览器之外的作用，同时增加了需要HTTP支持的应用程序的数量。

Exception in thread "main" java.lang.IllegalArgumentException: Illegal character in query at indexxx. 在请求第三方接口时发生了如下错误，并且参数格式都是正确的，通过翻阅一些资料，定位是请求前进行编码。

代码如下：

public static String post(String url , Map params) throws Exception {
        //String encode = URLEncoder.encode(JSON.toJSONString(params),"UTF-8");
        HttpClient client = HttpClients.createDefault();
        HttpPost httppost = new HttpPost(new StringBuilder().append(url+JSON.toJSONString(params).toString());
        logger.info(String.format("URI:%s",httppost.getURI()));
        HttpResponse res = client.execute(httppost);
        String result ="";
        HttpEntity entity = res.getEntity();
        if (entity != null)
            result = EntityUtils.toString(entity, "UTF-8");
        return result;
    }

错误：Exception in thread "main" java.lang.IllegalArgumentException: Illegal character in query at index 6.....

原因：参数需要编码后然后发送请求，完整代码如下：

public static String post(String url , Map params) throws Exception {
        String encode = URLEncoder.encode(JSON.toJSONString(params),"UTF-8");
        HttpClient client = HttpClients.createDefault();
        HttpPost httppost = new HttpPost(new StringBuilder().append(url+encode).toString());
        logger.info(String.format("URI:%s",httppost.getURI()));
        HttpResponse res = client.execute(httppost);
        String result ="";
        HttpEntity entity = res.getEntity();
        if (entity != null)
            result = EntityUtils.toString(entity, "UTF-8");
        return result;
    }

编码后的参数打印在控制台了：URI:http://xxxx:8080/testmethod=test&params=%7B%22vo%22%3A%7B%22shownum%22%3A

由于太长以上copy了一部分。

还有一种方式来请求：

URI uri = new URIBuilder()  
        .setScheme("http")  
        .setHost("www.google.com")  
        .setPath("/search")  
        .setParameter("q", "httpclient")  
        .setParameter("btnG", "Google Search")  
        .build();  
HttpGet httpget = new HttpGet(uri);  

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