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<title> [Golang] http.Request复用 | Domechn.</title>
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<div class="post-title animate__animated animate__fadeInUp">[Golang] http.Request复用</div>
<div class="meta-intro animate__animated animate__fadeInUp">Feb 21 2019</div>

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<h3 id="复用针对除了-Get-以外的请求"><a href="#复用针对除了-Get-以外的请求" class="headerlink" title="复用针对除了 Get 以外的请求"></a>复用针对除了 Get 以外的请求</h3><pre><code class="go">package main

import (
&quot;net/http&quot;
&quot;strings&quot;
)

func main()&#123;
reader := strings.NewReader(&quot;hello&quot;)
req,_ := http.NewRequest(&quot;POST&quot;,&quot;http://www.abc.com&quot;,reader)
client := http.Client&#123;&#125;
client.Do(req) // 第一次会请求成功
client.Do(req) // 请求失败
&#125;
</code></pre>
<p>第二次请求会出错</p>
<p><code>http: ContentLength=5 with Body length 0</code></p>
<p>原因是第一次请求后 req.Body 已经读取到结束位置，所以第二次请求时无法再读取 body，<br>解决方法：重新定义一个 ReadCloser 的实现类替换 req.Body</p>
<pre><code class="go">package reader

import (
&quot;io&quot;
&quot;net/http&quot;
&quot;strings&quot;
&quot;sync/atomic&quot;
)

type Repeat struct&#123;
reader io.ReaderAt
offset int64
&#125;

// Read 重写读方法，使每次读取request.Body时能从指定位置读取
func (p *Repeat) Read(val []byte) (n int, err error) &#123;
n, err = p.reader.ReadAt(val, p.offset)
atomic.AddInt64(&amp;p.offset, int64(n))
return
&#125;

// Reset 重置偏移量
func (p *Repeat) Reset()&#123;
atomic.StoreInt64(&amp;p.offset,0)
&#125;

func (p *Repeat) Close() error &#123;
// 因为req.Body实现了readcloser接口，所以要实现close方法
// 但是repeat中的值有可能是只读的，所以这里只是尝试关闭一下。
if p.reader != nil &#123;
if rc, ok := p.reader.(io.Closer); ok &#123;
return rc.Close()
&#125;
&#125;
return nil
&#125;

func doPost() &#123;
client := http.Client&#123;&#125;
reader := strings.NewReader(&quot;hello&quot;)
req , _ := http.NewRequest(&quot;POST&quot;,&quot;http://www.abc.com&quot;,reader)
req.Body = &amp;Repeat&#123;reader:reader,offset:0&#125;
client.Do(req)
// 将偏移量重置为0
req.Body.(*Repeat).Reset()
client.Do(req)
&#125;
</code></pre>
<p>这样就不会报错了，因为也重写了 Close()方法，所以同时也解决了 request 重用时，req.Body 自动关闭的问题。</p>

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