https://jizuiba.netlify.app/categories/%E8%B8%A9%E5%9D%91%E7%AC%94%E8%AE%B0/Recent content in 踩坑笔记 on Jizuiba`s BlogHugozh-cnThu, 10 Jul 2025 00:00:00 +0000https://jizuiba.netlify.app/posts/bean%E7%94%9F%E5%91%BD%E5%91%A8%E6%9C%9F%E7%AE%A1%E7%90%86%E9%94%99%E8%AF%AF%E6%A1%88%E4%BE%8B/Thu, 10 Jul 2025 00:00:00 +0000https://jizuiba.netlify.app/posts/bean%E7%94%9F%E5%91%BD%E5%91%A8%E6%9C%9F%E7%AE%A1%E7%90%86%E9%94%99%E8%AF%AF%E6%A1%88%E4%BE%8B/<h2 id="一错误案例">一、错误案例</h2> <figure class="article-codeblock article-codeblock--java" data-code-language="java" style="--code-max-height: 32rem;"><figcaption class="article-codeblock__header" aria-label="Code block tools"><button type="button" class="article-codeblock__copy" data-copy-default="复制" data-copy-success="已复制" data-copy-error="失败" aria-label="复制"> <svg class="article-codeblock__copy-icon" width="14" height="14" viewBox="0 0 24 24" aria-hidden="true"> <rect x="9" y="9" width="13" height="13" rx="2" ry="2"></rect> <path d="M5 15H4a2 2 0 0 1-2-2V4a2 2 0 0 1 2-2h9a2 2 0 0 1 2 2v1"></path> </svg> <span class="article-codeblock__copy-text">复制</span> </button><span class="article-codeblock__language" aria-label="Code language">java</span></figcaption><div class="article-codeblock__body"><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="nd">@Service</span><span class="w"> </span></span></span><span class="line"><span class="cl"><span class="nd">@Slf4j</span><span class="w"> </span></span></span><span class="line"><span class="cl"><span class="kd">public</span><span class="w"> </span><span class="kd">class</span> <span class="nc">MyService</span><span class="w"> </span><span class="p">{</span><span class="w"> </span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="nd">@Value</span><span class="p">(</span><span class="s">&#34;${resend.to}&#34;</span><span class="p">)</span><span class="w"> </span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="kd">private</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="n">to</span><span class="p">;</span><span class="w"> </span></span></span><span class="line"><span class="cl"><span class="w"> </span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="nf">MyService</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"> </span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="n">log</span><span class="p">.</span><span class="na">info</span><span class="p">(</span><span class="s">&#34;to =&gt; {}&#34;</span><span class="p">,</span><span class="w"> </span><span class="k">this</span><span class="p">.</span><span class="na">to</span><span class="p">);</span><span class="w"> </span><span class="c1">// 此时的to为null</span><span class="w"> </span></span></span><span class="line"><span class="cl"><span class="w"> </span><span class="p">}</span><span class="w"> </span></span></span><span class="line"><span class="cl"><span class="p">}</span></span></span></code></pre></div></div> </figure><p>Spring 调用构造函数（此时<code>to</code>还未注入，字段是<code>null</code>）。</p>