Java 使用EL表达式，但页面可以'；我不能正确地给出答案_Java_Jsp_Struts2_El

Java 使用EL表达式，但页面可以'；我不能正确地给出答案

java jsp struts2

Java 使用EL表达式，但页面可以'；我不能正确地给出答案,java,jsp,struts2,el,Java,Jsp,Struts2,El,这是Struts程序。我必须做一个登录页面。如果我在登录页面中输入名称itcast和密码123，则页面将转到success.jsp（我在此页面中失败），否则它将显示错误.jsp loginaction.java： package cn.itcast.action; import com.opensymphopensymphony.xwork2.ActionContext; import com.opensymphony.xwork2.ActionSupport; public class Log

这是Struts程序。我必须做一个登录页面。如果我在登录页面中输入名称

itcast

和密码

，则页面将转到

success.jsp

（我在此页面中失败），否则它将显示

错误.jsp

loginaction.java
：

package cn.itcast.action;
import com.opensymphopensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
public class LoginAction extends ActionSupport {
    private String username; 
    private String password; 
    
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    //@Override
    public String execute() throws Exception {
    
        ActionContext context = ActionContext.getContext();
        if ("itcast".equals(username) && "123".equals(password)) {
            
            context.put("username", username);//${username}<br>
            context.put("password", password); //${password} 
            context.put("success", "success");
            return SUCCESS;
        } else {
            
            context.put("error", "error_zdh");
            return ERROR;
        }
    }
}

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>login page</title>
</head>
<body>
    <div align="center">login page
        <form action="login" method="post">
            username:<input type="text" name="username" /><br> 
            password:<input
                type="password" name="password" /><br> <input type="submit"
                value="login" />
        </form>
    </div>
</body>
</html>

<%@ page language="java" import="java.util.*"    pageEncoding="utf-8"%>


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>failed page</title>
</head>
<body>
    <p>
        ${error }<br>
    </p>
</body>
</html>

<%@ page language="java" import="java.util.*"  pageEncoding="utf-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>success page</title>
</head>
<body>
    <p>
        ${success }<br>
    </p>
    <h2>login information</h2>
    username:${username }<br>
     password:${password }<br>
</body>
</html>

login.jsp
：

package cn.itcast.action;
import com.opensymphopensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
public class LoginAction extends ActionSupport {
    private String username; 
    private String password; 
    
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    //@Override
    public String execute() throws Exception {
    
        ActionContext context = ActionContext.getContext();
        if ("itcast".equals(username) && "123".equals(password)) {
            
            context.put("username", username);//${username}<br>
            context.put("password", password); //${password} 
            context.put("success", "success");
            return SUCCESS;
        } else {
            
            context.put("error", "error_zdh");
            return ERROR;
        }
    }
}

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>login page</title>
</head>
<body>
    <div align="center">login page
        <form action="login" method="post">
            username:<input type="text" name="username" /><br> 
            password:<input
                type="password" name="password" /><br> <input type="submit"
                value="login" />
        </form>
    </div>
</body>
</html>

<%@ page language="java" import="java.util.*"    pageEncoding="utf-8"%>


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>failed page</title>
</head>
<body>
    <p>
        ${error }<br>
    </p>
</body>
</html>

<%@ page language="java" import="java.util.*"  pageEncoding="utf-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>success page</title>
</head>
<body>
    <p>
        ${success }<br>
    </p>
    <h2>login information</h2>
    username:${username }<br>
     password:${password }<br>
</body>
</html>

success.jsp
：

package cn.itcast.action;
import com.opensymphopensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionSupport;
public class LoginAction extends ActionSupport {
    private String username; 
    private String password; 
    
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    //@Override
    public String execute() throws Exception {
    
        ActionContext context = ActionContext.getContext();
        if ("itcast".equals(username) && "123".equals(password)) {
            
            context.put("username", username);//${username}<br>
            context.put("password", password); //${password} 
            context.put("success", "success");
            return SUCCESS;
        } else {
            
            context.put("error", "error_zdh");
            return ERROR;
        }
    }
}

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>login page</title>
</head>
<body>
    <div align="center">login page
        <form action="login" method="post">
            username:<input type="text" name="username" /><br> 
            password:<input
                type="password" name="password" /><br> <input type="submit"
                value="login" />
        </form>
    </div>
</body>
</html>

<%@ page language="java" import="java.util.*"    pageEncoding="utf-8"%>


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>failed page</title>
</head>
<body>
    <p>
        ${error }<br>
    </p>
</body>
</html>

<%@ page language="java" import="java.util.*"  pageEncoding="utf-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>success page</title>
</head>
<body>
    <p>
        ${success }<br>
    </p>
    <h2>login information</h2>
    username:${username }<br>
     password:${password }<br>
</body>
</html>


成功页面

${success}


登录信息
用户名：${username}

密码：${password}

您误解了

ActionContext

的概念。您应该区分操作上下文和

ValueStack

。请参阅答案以澄清问题

每个地方都有其专用的存储空间，您可以在其中放置对象以供以后在某个调用上下文中运行/检索。运行框架的任何上下文都是关联的。上下文是在它内部的作用域对象之间进行通信的方式，您可以使用Java或其他表达式语言（EL）如OGNL进行访问

在OGNL中，操作上下文是OGNL上下文，值堆栈是根

框架将OGNL上下文设置为我们的

ActionContext

，将值堆栈设置为OGNL根对象。（值堆栈是由多个对象组成的集合，但对OGNL而言，它似乎是单个对象。）与值堆栈一起，框架将其他对象放置在

ActionContext

中，包括表示应用程序、会话和请求上下文的

Map

s。这些对象与值堆栈（我们的OGNL根）一起共存于

ActionContext

由于重定向到JSP页面，将调用新操作并创建新的

ActionContext

对象。它不保留以前上下文中的值

您需要的是保存一些值，比如一个会话，您可以通过实现

SessionAware

或直接使用API来正常注入该会话。请参阅答案以了解哪些上下文对象可用于Struts2应用程序

要使用Struts会话映射，您应该在操作中实现

SessionAware

。因此，将向其注入会话，然后您可以使用会话映射来放置这些值，这些值可以通过OGNL访问

SessionAware

实现示例：

private Map<String, Object> session;

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

私有映射会话；
@凌驾
公共无效设置会话（映射会话）{
this.session=会话；
}

看