????? 在搭建spring mvc rest环境时遇些问题:

问题1:

????? 当Controller返回Object时，请求json数据返回的内容和我期望的不一致，例如返回的Object是User类有个name属性，原本希望返回{"name":'姓名'}这样的数据，结果返回{"user":{"name":"姓名"}}。

问题原因:

????? org.springframework.web.servlet.view.json.MappingJacksonJsonView类的filterModel方法返回的是key为user的Map对象，而实际我想要的效果是直接返回User对象。

解决办法:

????? 继承MappingJacksonJsonView类，重写filterModel方法

protected Object filterModel(Map<String, Object> model) {
  Map<?, ?> result = (Map<?, ?>) super.filterModel(model);
  if (result.size() == 1) {
    return result.values().iterator().next();
  }else{
    return result;
  }
}

问题2:

????? 当Controller返回Object时，请求xml数据返回的内容和预期的不一致。Controller明明返回的是User结果xml返回的是org.springframework.validation.BindingResult对象

问题原因:

????? org.springframework.web.servlet.view.xml.MarshallingView类的locateToBeMarshalled方法接受的参数Map<String, Object> model里有2个对象分别是BindingResult和User，locateToBeMarshalled方法在返回时候先检索到BindingResult结果就返回了它而不是真正需要返回的User

for (Object o : model.values()) {
  if (o != null && this.marshaller.supports(o.getClass())) {
    return o;，
  }
}

解决办法:

????? 继承MarshallingView类重写locateToBeMarshalled方法，由于MarshallingView类没有提供marshaller,和modelKey的get方法，所以还要重写这2个属性相关的内容，完整代码如下

public class MarshallingView extends org.springframework.web.servlet.view.xml.MarshallingView{

  private Marshaller marshaller;

  private String modelKey;

  public Marshaller getMarshaller() {
    return marshaller;
  }

  public String getModelKey() {
    return modelKey;
  }

  public MarshallingView() {
    super();
  }

  public MarshallingView(Marshaller marshaller) {
    super(marshaller);
    this.marshaller = marshaller;
  }

  @Override
  public void setMarshaller(Marshaller marshaller) {
    super.setMarshaller(marshaller);
    this.marshaller = marshaller;
  }

  @Override
  public void setModelKey(String modelKey) {
    super.setModelKey(modelKey);
    this.modelKey = modelKey;
  }

  @Override
  protected Object locateToBeMarshalled(Map<String, Object> model) throws ServletException {
    if (this.getModelKey() != null) {
      Object o = model.get(this.getModelKey());
      if (o == null) {
        throw new ServletException("Model contains no object with key [" + modelKey + "]");
      }
      if (!this.getMarshaller().supports(o.getClass())) {
        throw new ServletException("Model object [" + o + "] retrieved via key [" + modelKey +
            "] is not supported by the Marshaller");
      }
      return o;
    }

    for (Object o : model.values()) {
      if (o != null && !(o instanceof BindingResult) && this.getMarshaller().supports(o.getClass())) {
        return o;
      }
    }
    return null;
  }
}

?其实关键的修改只有

!(o instanceof BindingResult)

这一句，在返回时候跳过BindingResult类。

?