可以使用Interceptor来修改请求体，将getter转换为可用于POST请求的数据格式。

以下是一个示例Interceptor：

import { Injectable } from '@angular/core';
import { HttpInterceptor, HttpRequest, HttpHandler } from '@angular/common/http';

@Injectable()
export class GetterInterceptor implements HttpInterceptor {
  intercept(req: HttpRequest, next: HttpHandler) {
    // 如果请求方法是POST并且请求体中包含getter，则将其转换为普通的数据对象
    if (req.method === 'POST' && req.body instanceof Object) {
      let newBody = {};
      for (let key in req.body) {
        if (req.body.hasOwnProperty(key)) {
          let value = req.body[key];
          if (typeof value === 'function') {
            // 调用getter并将结果作为普通值添加到请求体中
            newBody[key] = value();
          } else {
            newBody[key] = value;
          }
        }
      }
      // 修改请求对象的body
      req = req.clone({
        body: newBody
      });
    }
    return next.handle(req);
  }
}

在需要使用该Interceptor的模块中，将其提供给HttpClientModule：

import { NgModule } from '@angular/core';
import { HttpClientModule, HTTP_INTERCEPTORS } from '@angular/common/http';
import { GetterInterceptor } from './getter.interceptor';

@NgModule({
  imports: [
    HttpClientModule
  ],
  providers: [
    {
      provide: HTTP_INTERCEPTORS,
      useClass: GetterInterceptor,
      multi: true
    }
  ]
})
export class MyModule { }

这样，在发送POST请求时，就可以将getter作为请求体的一部分发送了：

import { HttpClient } from '@angular/common/http';

class MyService {
  constructor(private httpClient: HttpClient) {}

  save(model: MyModel) {
    return this.httpClient.post('/api/save', model);
  }
}

class MyModel {
  name: string;
  get age() {
    return this._age;
  }
  set age(value: number) {
    this._age = value;
  }