struts2--模型驱动

其实模型驱动这个名字听起来挺大气的 说实话乍看起来看不明白。

先举例：一个model类：Department类，就是一个简单的类。

public class Department implements Serializable{

    private Long did;
    private String dname;
    private String description;
    
    private Set<User> users;

    public Long getDid() {
        return did;
    }

    public void setDid(Long did) {
        this.did = did;
    }

    public String getDname() {
        return dname;
    }

    public void setDname(String dname) {
        this.dname = dname;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public Set<User> getUsers() {
        return users;
    }

    public void setUsers(Set<User> users) {
        this.users = users;
    }
    
}

既然是说明struts2的模型驱动，当然得再建一个action类DepartmentAction.class

public class DepartmentAction extends ActionSupport implements ModelDriven<Department>{

    private IDepartmentService departmentService;
    
    private Department department = new Department();
    public void setDepartmentService(IDepartmentService departmentService) {
        this.departmentService = departmentService;
    }
    public Department getModel() {
        return department;
    }     
    
}

该类继承了ActionSupport类，实现了接口ModelDriven,这个接口定义了一个方法叫做getModel(),它是用来返回实体的对象，像上面的department。

到底getModel方法谁来调用，那就是拦截器来调用。模型驱动拦截器ModelDrivenInterceptor中的部分源码

@Override
    public String intercept(ActionInvocation invocation) throws Exception {
        Object action = invocation.getAction();

        if (action instanceof ModelDriven) {//判断当前的action是否实现了ModelDriven接口
            ModelDriven modelDriven = (ModelDriven) action;
            ValueStack stack = invocation.getStack();//把ValueStack值栈取出来
            Object model = modelDriven.getModel();
            if (model !=  null) {
                stack.push(model);//把模型驱动的对象加入到栈顶
            }
            if (refreshModelBeforeResult) {
                invocation.addPreResultListener(new RefreshModelBeforeResult(modelDriven, model));
            }
        }
        return invocation.invoke();
    }