What you want to do (purpose)

Map Spring GET request (URL parameter) to complex object (Bean).

--Nested structure --List structure

Conclusion

Do not use annotations for Mapping. Or Use @ModelAttribute.

It is necessary to match the key of the variable name and the URL parameter.

environment

Spring Boot:2.1.6

Other libraries used

lombok

Textile verification source

Mapping destination

Parent object

@Data
@ToString
public class ComplexBean {
  private String hoge;
  private ChildBean childBean;
  private List<ItemBean> itemBeans;
}

Child object for nesting

@Data
@ToString
public class ChildBean {
  private String piyo;
}

Object for list

@Data
@ToString
public class ItemBean {
  private String fuga;
}

@Data and @ToString are annotations of lombok @ToString is for verification

controller

@RestController
public class DemoRestController {

  @GetMapping(value = "/param")
  @ResponseBody
  public String getParam(@RequestParam ComplexBean bean) {
    System.out.println(bean.toString());
    return bean.toString();
  }

  @GetMapping(value = "/model")
  @ResponseBody
  public String getModel(@ModelAttribute ComplexBean bean) {
    System.out.println(bean.toString());
    return bean.toString();
  }

  @GetMapping(value = "/direct")
  @ResponseBody
  public String getDirect(ComplexBean bean) {
    System.out.println(bean.toString());
    return bean.toString();
  }
}

Verification

Restlet Client-Access each endpoint using REST API Testing

URL parameters to validate

hoge=hoge&childBean.piyo=piyo&itemBeans[0].fuga=fuga0&itemBeans[2].fuga=fuga2

result

When using @RequestParam (http://localhost:8080/param?hoge=hoge&childBean.piyo=piyo&itemBeans[0].fuga=fuga0&itemBeans[2].fuga=fuga2) Since the mapping information is insufficient, parsing cannot be performed and an error occurs.

Resolved [org.springframework.web.bind.MissingServletRequestParameterException: Required ComplexBean parameter 'bean' is not present]

When using @ModelAttribute (http://localhost:8080/model?hoge=hoge&childBean.piyo=piyo&itemBeans[0].fuga=fuga0&itemBeans[2].fuga=fuga2) Mapped as expected.

Without annotation (http://localhost:8080/direct?hoge=hoge&childBean.piyo=piyo&itemBeans[0].fuga=fuga0&itemBeans[2].fuga=fuga2) Mapped as expected.

Summary

Even with URL parameters that have the following structure --Nested structure --List structure