Struts2学习（五）访问web元素总结

struts2访问web元素（request、session、application）有4中方法，下面来介绍下这4种方法。前两种是取得Map类型request,session,application,后两种是真实类型 HttpServletRequest, HttpSession, ServletContext的引用。其中map类型中第二种方法是最常用的，其他三种知道就行一般不会用到。

第一种方式：

依赖于struts2容器，自己取值

package com.bjsxt.struts2.user.action;
import java.util.Map;
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
public class LoginAction1 extends ActionSupport {
    private Map request;
    private Map session;
    private Map application;

    public LoginAction1() {
        request = (Map)ActionContext.getContext().get("request");
        session = ActionContext.getContext().getSession();
        application = ActionContext.getContext().getApplication();
    }

    public String execute() {
        request.put("r1", "r1");
        session.put("s1", "s1");
        application.put("a1", "a1");
        return SUCCESS; 
    }
}

第二种方式：

使用DI（依赖注入）IOC（控制反转）的思想自动获取，不用自己初始化，继承借口即可，元素会被自动初始化赋值。

package com.bjsxt.struts2.user.action;
import java.util.Map;
import org.apache.struts2.interceptor.ApplicationAware;
import org.apache.struts2.interceptor.RequestAware;
import org.apache.struts2.interceptor.SessionAware;
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;

public class LoginAction2 extends ActionSupport implements RequestAware,SessionAware, ApplicationAware {

    private Map<String, Object> request;
    private Map<String, Object> session;
    private Map<String, Object> application;

    //DI dependency injection
    //IoC inverse of control
    public String execute() {
        request.put("r1", "r1");
        session.put("s1", "s1");
        application.put("a1", "a1");
        return SUCCESS; 
    }

    @Override
    public void setRequest(Map<String, Object> request) {
        this.request = request;
    }

    @Override
    public void setSession(Map<String, Object> session) {
        this.session = session;
    }

    @Override
    public void setApplication(Map<String, Object> application) {
        this.application = application;
    }


}

第三种方式：

package com.bjsxt.struts2.user.action;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import org.apache.struts2.ServletActionContext;
import com.opensymphony.xwork2.ActionSupport;

public class LoginAction3 extends ActionSupport {

    private HttpServletRequest request;
    private HttpSession session;
    private ServletContext application;

    public LoginAction3() {
        request = ServletActionContext.getRequest();
        session = request.getSession();
        application = session.getServletContext();
    }

    public String execute() {
        request.setAttribute("r1", "r1");
        session.setAttribute("s1", "s1");
        application.setAttribute("a1", "a1");
        return SUCCESS; 
    }

}

第四种方式：

package com.bjsxt.struts2.user.action;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import org.apache.struts2.interceptor.ServletRequestAware;
import com.opensymphony.xwork2.ActionSupport;

public class LoginAction4 extends ActionSupport implements ServletRequestAware {

    private HttpServletRequest request;
    private HttpSession session;
    private ServletContext application;

    public String execute() {
        request.setAttribute("r1", "r1");
        session.setAttribute("s1", "s1");
        application.setAttribute("a1", "a1");
        return SUCCESS; 
    }

    @Override
    public void setServletRequest(HttpServletRequest request) {
        this.request = request;
        this.session = request.getSession();
        this.application = session.getServletContext();
    }

}

当然，通过这些方法取得web元素，基本上只会用到session，大家知道request请求的参数可以通过属性自动接收，这是struts2的自己的特点。