通过扩展Sturts2中的ResultType，使json深度整合Struts2。
实体：
```
public class Category implements Serializable {
private static final long serialVersionUID = -8235767662633687654L;
private String id;
private String name;
private Boolean commend;
private Category parent;
private Content content;
private Group group;
private Set
children;
private Set articles;
private Set authoritys;
```
CategoryAction类：
```
public class CategoryAction extends ActionSupport {
private static final long serialVersionUID = -7390334268442171137L;
private Collection categorys;
```
Struts.xml
```
