Struts2中的ModelDriven接口

若没有实现ModelDriven的接口，Controll的代码会比较冗余，不能实现Controll和Model代码的分离

下面是没有实现ModelDriven接口的SuggestAction

package dayday.controll;

import com.opensymphony.xwork2.ActionSupport;
import com.opensymphony.xwork2.ModelDriven;
import dayday.model.Product;
import dayday.model.Suggest;
import dayday.service.AddSuggest;

/**
 * Created by I am master on 2017/2/22.
 */
public class SuggestAction extends ActionSupport{
    //保存对象的信息
    private Suggest suggest;
    private AddSuggest addSuggest;

    private String sugName;
    private String sugEmail;
    private String sugPhone;
    private String sugContent;

    public String getSugName() {
        return sugName;
    }

    public void setSugName(String sugName) {
        this.sugName = sugName;
    }

    public String getSugEmail() {
        return sugEmail;
    }

    public void setSugEmail(String sugEmail) {
        this.sugEmail = sugEmail;
    }

    public String getSugPhone() {
        return sugPhone;
    }

    public void setSugPhone(String sugPhone) {
        this.sugPhone = sugPhone;
    }

    public String getSugContent() {
        return sugContent;
    }

    public void setSugContent(String sugContent) {
        this.sugContent = sugContent;
    }

    @Override
    public String execute()throws Exception{
        suggest.setSugContent(getSugContent());
        suggest.setSugEmail(getSugEmail());
        suggest.setSugName(getSugName());
        suggest.setSugPhone(getSugPhone());
        addSuggest.insertSuggest(suggest);
        return SUCCESS;
    }
}

实现了ModelDriven接口的SuggestAction接口以后的代码

package dayday.controll;

import com.opensymphony.xwork2.ActionSupport;
import com.opensymphony.xwork2.ModelDriven;
import dayday.model.Product;
import dayday.model.Suggest;
import dayday.service.AddSuggest;

/**
 * Created by I am master on 2017/2/22.
 */
public class SuggestAction extends ActionSupport implements ModelDriven<Suggest>{
    //保存对象的信息
    private Suggest suggest;
    private AddSuggest addSuggest;
    

    @Override
    public String execute()throws Exception{
        addSuggest.insertSuggest(suggest);
        return SUCCESS;
    }

    @Override
    public Suggest getModel() {
        suggest=new Suggest();
        return suggest;
    }
}

明显代码量减少了很多，实现了分离

Action实现ModelDriven接口运行的原理

1). 先会执行 ModelDrivenInterceptor 的 intercept 方法. 

    public String intercept(ActionInvocation invocation) throws Exception {
        //获取 Action 对象: SuggestAction 对象, 此时该 Action 已经实现了 ModelDriven 接口
        //public class SuggestAction extends ActionSupport, implements ModelDriven<Employee>
        Object action = invocation.getAction();

        //判断 action 是否是 ModelDriven 的实例
        if (action instanceof ModelDriven) {
            //强制转换为 ModelDriven 类型
            ModelDriven modelDriven = (ModelDriven) action;
            //获取值栈
            ValueStack stack = invocation.getStack();
            //调用 ModelDriven 接口的 getModel() 方法
            //即调用 EmployeeAction 的 getModel() 方法
            /*
            public Employee getModel() {
                employee = new Employee();
                return employee;
            }
            */
            Object model = modelDriven.getModel();
            if (model !=  null) {
                //把 getModel() 方法的返回值压入到值栈的栈顶. 实际压入的是 EmployeeAction 的 employee 成员变量
                stack.push(model);
            }
            if (refreshModelBeforeResult) {
                invocation.addPreResultListener(new RefreshModelBeforeResult(modelDriven, model));
            }
        }
        return invocation.invoke();
    }
   
2). 执行 ParametersInterceptor 的 intercept 方法: 把请求参数的值赋给栈顶对象对应的属性. 若栈顶对象没有对应的属性, 则查询
值栈中下一个对象对应的属性...

3). 注意: getModel 方法不能提供以下实现. 的确会返回一个 Suggest 对象到值栈的栈顶. 但当前 Action 
的 suggest 成员变量却是 null. 

public Suggest getModel() {
    return new Suggest();
}