如何让Fastify部分路由使用不同的fastify-multipart配置？

你可以通过分前缀注册fastify-multipart插件实现不同路由的差异化配置：

1. 为全局路由（排除/image/*）注册插件并启用addToBody: true
2. 单独为/image/*前缀注册插件，禁用addToBody（不设置该选项或显式设为false）

插件注册代码 #

// 全局注册（跳过/image/*路由），开启addToBody
app.register(require("fastify-multipart"), { 
  addToBody: true,
  onRequest: (request, _, done) => {
    if (request.url.startsWith('/image/')) {
      done(new Error('skip')); // 跳过当前插件逻辑
    } else {
      done();
    }
  }
});

// 为/image/*路由单独注册，禁用addToBody
app.register(require("fastify-multipart"), { 
  addToBody: false 
}, { prefix: '/image' });

路由定义保持不变 #

app.get("/health", (_, reply) => reply.send("Congratulations! reverse proxy is working....."));

app.route({
  method: ["DELETE", "GET", "HEAD", "PATCH", "POST", "PUT"],
  url: "*",
  handler: handler,
});

修复后的/image/upload处理函数 #

原处理函数存在几个潜在问题，调整后如下：

const FormData = require('form-data'); // 需要先安装form-data包

const handler = async (request, reply) => {
  const formData = new FormData();
  let uploadError = null;

  return new Promise((resolve, reject) => {
    const multipart = request.multipart(
      (field, stream, filename, _, mimetype) => {
        // 传递文件信息给FormData
        formData.append('image', stream, { filename, mimetype });
      },
      (error) => {
        if (error) {
          uploadError = error;
          console.log(`Error uploading file: ${error.message}`);
          reply.code(500).send();
          reject(error);
        }
      }
    );

    // 等待multipart解析完成后再发送请求
    multipart.on('end', async () => {
      if (uploadError) return;
      try {
        const config = {
          headers: { ...formData.getHeaders() } // 必须携带FormData的请求头
        };
        const data = await axios.post('http://127.0.0.1:80/downstream', formData, config);
        console.log("upload success with url", data);
        reply.send(data);
        resolve(data);
      } catch (e) {
        console.log(`An error occurred during upload: ${e.message}`);
        reply.code(500).send();
        reject(e);
      }
    });
  });
};

原理说明 #

• Fastify支持按路由前缀注册插件，不同前缀的插件配置相互独立，不会冲突
• 全局插件通过onRequest钩子跳过/image/*路由的处理，避免干扰前缀插件的逻辑
• /image/*路由下的插件禁用addToBody，保留原始multipart流，让request.multipart可以正常解析处理

内容的提问来源于stack exchange，提问作者Ashok Singh