HttpServletRequest:Get Session-阿里云开发者社区

1. HttpServletRequest.getSession

1.1 HttpServletRequest

接口HttpServletRequest继承自ServletRequest。

HttpServletRequest extends the javax.servlet.ServletRequest interface to provide request information for HTTP servlets.—— From javadoc

客户端浏览器发出的请求，会被封装成为一个HttpServletRequest对象。

请求的所有的信息，包括请求的地址、请求的参数、提交的数据、上传的文件、客户端的ip，甚至客户端操作系统都包含在其内。

servlet容器会创建一个HttpServletRequest对象，并将其转换为servlet的service、doGet、 doPost等方法的参数。

The servlet container creates an HttpServletRequest object and passes it as an argument to the servlet's service methods (doGet, doPost, etc).—— From javadoc

与Request相对的，HttpServletResponse继承了ServletResponse接口，并提供了与Http协议有关的方法，这些方法的主要功能是设置HTTP状态码和管理Cookie等。

1.2 getSession

HttpServletRequest 提供了两个重载的getSession方法，分别是getSession()和getSession(boolean create)。

getSession()和getSession(true)是相同的，都是获取当前客户端的Session，如果获取不到则创建一个新的Session返回。

getSession(false)，也是获取当前客户端的Session，不同的是，如果获取不到则返回null。

getSession
HttpSession getSession()
Gets the HttpSession connected with the client sending the request. If the client didn't have a session connected with him then a new HttpSession will be created. To maintain a session this method must be called before the connection is flushed or closed. Same as calling getSession(true).
Returns:
The HttpSession connected with the client sending the request.
Since:2.1getSession
HttpSession getSession(boolean create)
Gets the HttpSession connected with the client sending the request. If the client didn't have a session connected with him, and create is true then a new HttpSession will be created. If create is false then null is returned. To maintain a session this method must be called before the connection is flushed or closed.
Returns:
The HttpSession connected with the client sending the request.
Since:2.0
—— From javadoc

1.3 getSession() VS. getSession(boolean create)

在大多数场景下，getSession方法的目的是获取当前请求客户端的Session，然后设置或者获取属性。

如果获取不到当前请求客户端的Session，那么重新创建一个Session，一般情况下意义不大，纯属浪费。

因此推荐使用getSession(false)的方式来获取Session，注意先判空再使用即可，下面会详细介绍。

2. springmvc-session.xml

2.1 SessionUtil

通常从Session里存取属性的代码如下:

HttpSession session=request.getSession(false);
session.setAttribute("bar", new Long("1024"));
Object foo=session.getAttribute("foo");

可以抽取为工具类SessionUtil：

public final class SessionUtil{
  public static void setAttribute(HttpServletRequest request,String attributeName,Serializable attributeValue){
    request.getSession().setAttribute(attributeName, attributeValue);
  }
  public static <T> T getAttribute(HttpServletRequest request,String attributeName){
      Validate.notNull(request, "request can't be null!");
      HttpSession session = request.getSession(false);
      return session == null ? null : (T) session.getAttribute(attributeName);
  }
}

2.2 SessionAccessor

为了便于统一管理Session，可以将存取Session属性统一配置在XML中，实现和使用方式如下。

SessionUtil

import java.io.Serializable;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
public final class SessionUtil{
    public static <T> T getAttribute(HttpServletRequest request,String attributeName){
        HttpSession session = request.getSession(false);
        return session == null ? null : (T) session.getAttribute(attributeName);
    }
    public static void setAttribute(HttpServletRequest request,String attributeName,Serializable attributeValue){
        request.getSession().setAttribute(attributeName, attributeValue);
    }
    public static void removeAttribute(HttpServletRequest request,String attributeName){
        HttpSession session = request.getSession(false);
        if (null == session){
            return;
        }
        session.removeAttribute(attributeName);
    }
    /**
     * 遍历session的attribute,将 name /attributeValue 存入到map里.
     */
    public static Map<String, Serializable> getAttributeMap(HttpSession session){
        Map<String, Serializable> map = new HashMap<String, Serializable>();
        Enumeration<String> attributeNames = session.getAttributeNames();
        while (attributeNames.hasMoreElements()){
            String name = attributeNames.nextElement();
            map.put(name, (Serializable) session.getAttribute(name));
        }
        return map;
    }
    private SessionUtil(){
        throw new AssertionError("can not creat " + getClass().getName() + " instance");
    }
}

Accessible

import java.io.Serializable;
import javax.servlet.http.HttpServletRequest;
public interface Accessible{
    public void save(String key,Serializable serializable,HttpServletRequest request);
    public <T extends Serializable> T get(String key,HttpServletRequest request);
    public void remove(String key,HttpServletRequest request);
}

AbstractSessionAccessor

import java.io.Serializable;
import javax.servlet.http.HttpServletRequest;
import com.feilong.servlet.http.SessionUtil;
public class AbstractSessionAccessor implements Accessible{
    @Override
    public void save(String key,Serializable serializable,HttpServletRequest request){
        SessionUtil.setAttribute(request, key, serializable);
    }
    @Override
    public <T extends Serializable> T get(String key,HttpServletRequest request){
        return SessionUtil.getAttribute(request, key);
    }
    @Override
    public void remove(String key,HttpServletRequest request){
        SessionUtil.removeAttribute(request, key);
    }
}

SessionAccessor

package demo.session;
import java.io.Serializable;
import javax.servlet.http.HttpServletRequest;
public class SessionAccessor extends AbstractSessionAccessor{
    private String key;
    public void save(Serializable serializable,HttpServletRequest request){
        super.save(key, serializable, request);
    }
    public <T extends Serializable> T get(HttpServletRequest request){
        return super.get(key, request);
    }
    public void remove(HttpServletRequest request){
        super.remove(key, request);
    }
    public SessionAccessor(){}
    public SessionAccessor(String key){
        this.key = key;
    }
    public void setKey(String key){
        this.key = key;
    }
    public String getKey(){
        return key;
    }
}

springmvc-session.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:aop="http://www.springframework.org/schema/aop" xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.3.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.3.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.3.xsd
        ">
    <bean name="fooSessionAccessor" class="demo.session.SessionAccessor">
        <property name="key" value="attr_name_foo" />
    </bean>
</beans>

FooController

@Controller
public class FooController extends BaseController{
    @Autowired
    @Qualifier("fooSessionAccessor")
    private SessionAccessor fooSessionAccessor;
    @ResponseBody
    @RequestMapping(value = "/root/path/foo",method = RequestMethod.POST)
        public Object foo(HttpServletRequest request,HttpServletResponse response){
        guestKeySessionAccessor.save("value1", request);
        guestKeySessionAccessor.get(request);
        guestKeySessionAccessor.remove(request);
     }
}

参考链接

搜狗百科 - httpservletrequest

GNU-javadoc-HttpServletRequest

HttpServletRequest:Get Session

1. HttpServletRequest.getSession

1.1 HttpServletRequest

1.2 getSession

1.3 getSession() VS. getSession(boolean create)

2. springmvc-session.xml

2.1 SessionUtil

2.2 SessionAccessor

参考链接

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插件

HttpServletRequest:Get Session

1. HttpServletRequest.getSession

1.1 HttpServletRequest

1.2 getSession

1.3 getSession() VS. getSession(boolean create)

2. springmvc-session.xml

2.1 SessionUtil

2.2 SessionAccessor

参考链接

热门文章

最新文章

相关电子书