springsecurity 之 登录用户数据的获取
springsecurity 中，用户登录信息本质是保存到 HttpSession 中，springsecurity 进行封装 获取登录数据有两种思路：
从 SecurityContextHolder 中获取
从当前请求对象中获取
从 SecurityContextHolder 中获取
@RestControllerpublic class HelloController { @GetMapping("/hello") public void hello() { Authentication authentication = SecurityContextHolder.getContext().getAuthentication(); System.out.println("authentication.getClass() = " + authentication.getClass()); }}
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SecurityContextHolder 存放的是 SecurityContext ，SecurityContextHolder 中定义三种不同的数据存储策略，采用了策略模式
MODE_THREADLOCAL ：将 SecurityContext 放在 ThreadLocal 中，开启子线程，子线程获取不到用户数据。
MODE_INHERITABLETHREADLOCAL：多线程环境，子线程也能获取到用户数据。
MODE_GLOBAL：数据保存到一个静态变量中，web 开发中很少使用。
SecurityContextHolderStrategy 接口用来规范存储策略中的方法
public interface SecurityContextHolderStrategy { void clearContext();
SecurityContext getContext();
void setContext(SecurityContext var1);
SecurityContext createEmptyContext();}
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有三个实现类 对应三个不同的存储策略
ThreadLocalSecurityContextHolderStrategy
//// Source code recreated from a .class file by IntelliJ IDEA// (powered by FernFlower decompiler)//
package org.springframework.security.core.context;
import org.springframework.util.Assert;
final class ThreadLocalSecurityContextHolderStrategy implements SecurityContextHolderStrategy { private static final ThreadLocal<SecurityContext> contextHolder = new ThreadLocal();
ThreadLocalSecurityContextHolderStrategy() { }
public void clearContext() { contextHolder.remove(); }
public SecurityContext getContext() { SecurityContext ctx = (SecurityContext)contextHolder.get(); if (ctx == null) { ctx = this.createEmptyContext(); contextHolder.set(ctx); }
return ctx; }
public void setContext(SecurityContext context) { Assert.notNull(context, "Only non-null SecurityContext instances are permitted"); contextHolder.set(context); }
public SecurityContext createEmptyContext() { return new SecurityContextImpl(); }}
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存储载体是 ThreadLocal 针对 SecurityContext 的操作都是在 ThreadLocal 中进行操作。SecurityContext 只是个接口，只有一个实现类是 SecurityContextImpl
InheritableThreadLocalSecurityContextHolderStrategy
//// Source code recreated from a .class file by IntelliJ IDEA// (powered by FernFlower decompiler)//
package org.springframework.security.core.context;
import org.springframework.util.Assert;
final class InheritableThreadLocalSecurityContextHolderStrategy implements SecurityContextHolderStrategy { private static final ThreadLocal<SecurityContext> contextHolder = new InheritableThreadLocal();
InheritableThreadLocalSecurityContextHolderStrategy() { }
public void clearContext() { contextHolder.remove(); }
public SecurityContext getContext() { SecurityContext ctx = (SecurityContext)contextHolder.get(); if (ctx == null) { ctx = this.createEmptyContext(); contextHolder.set(ctx); }
return ctx; }
public void setContext(SecurityContext context) { Assert.notNull(context, "Only non-null SecurityContext instances are permitted"); contextHolder.set(context); }
public SecurityContext createEmptyContext() { return new SecurityContextImpl(); }}
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存储载体为 InheritableThreadLocal ，InheritableThreadLocal 继承 ThreadLocal，多了一个特性，就是在子线程创建的时间，会自动将父线程的数据复制到子线程中。实现了子线程中能够获取登录数据的功能。
GlobalSecurityContextHolderStrategy
//// Source code recreated from a .class file by IntelliJ IDEA// (powered by FernFlower decompiler)//
package org.springframework.security.core.context;
import org.springframework.util.Assert;
final class GlobalSecurityContextHolderStrategy implements SecurityContextHolderStrategy { private static SecurityContext contextHolder;
GlobalSecurityContextHolderStrategy() { }
public void clearContext() { contextHolder = null; }
public SecurityContext getContext() { if (contextHolder == null) { contextHolder = new SecurityContextImpl(); }
return contextHolder; }
public void setContext(SecurityContext context) { Assert.notNull(context, "Only non-null SecurityContext instances are permitted"); contextHolder = context; }
public SecurityContext createEmptyContext() { return new SecurityContextImpl(); }}
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存储载体是一个静态变量，也可以在多线程环境下使用，但用的较少。
SecurityContextHolder 源码
//// Source code recreated from a .class file by IntelliJ IDEA// (powered by FernFlower decompiler)//
package org.springframework.security.core.context;
import java.lang.reflect.Constructor;import org.springframework.util.ReflectionUtils;import org.springframework.util.StringUtils;
public class SecurityContextHolder { public static final String MODE_THREADLOCAL = "MODE_THREADLOCAL"; public static final String MODE_INHERITABLETHREADLOCAL = "MODE_INHERITABLETHREADLOCAL"; public static final String MODE_GLOBAL = "MODE_GLOBAL"; public static final String SYSTEM_PROPERTY = "spring.security.strategy"; private static String strategyName = System.getProperty("spring.security.strategy"); private static SecurityContextHolderStrategy strategy; private static int initializeCount = 0;
public SecurityContextHolder() { }
public static void clearContext() { strategy.clearContext(); }
public static SecurityContext getContext() { return strategy.getContext(); }
public static int getInitializeCount() { return initializeCount; }
private static void initialize() { if (!StringUtils.hasText(strategyName)) { strategyName = "MODE_THREADLOCAL"; }
if (strategyName.equals("MODE_THREADLOCAL")) { strategy = new ThreadLocalSecurityContextHolderStrategy(); } else if (strategyName.equals("MODE_INHERITABLETHREADLOCAL")) { strategy = new InheritableThreadLocalSecurityContextHolderStrategy(); } else if (strategyName.equals("MODE_GLOBAL")) { strategy = new GlobalSecurityContextHolderStrategy(); } else { try { Class<?> clazz = Class.forName(strategyName); Constructor<?> customStrategy = clazz.getConstructor(); strategy = (SecurityContextHolderStrategy)customStrategy.newInstance(); } catch (Exception var2) { ReflectionUtils.handleReflectionException(var2); } }
++initializeCount; }
public static void setContext(SecurityContext context) { strategy.setContext(context); }
public static void setStrategyName(String strategyName) { SecurityContextHolder.strategyName = strategyName; initialize(); }
public static SecurityContextHolderStrategy getContextHolderStrategy() { return strategy; }
public static SecurityContext createEmptyContext() { return strategy.createEmptyContext(); }
public String toString() { return "SecurityContextHolder[strategy='" + strategyName + "'; initializeCount=" + initializeCount + "]"; }
static { initialize(); }}
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SecurityContextHolder 定义三个静态常量描述三种不同存储策略，在静态代码块中初始化，根据不同的 strategyName 初始化不同的存储策略，可以调用配置系统变量或者调用 setStrategyName 改变策略。
在默认情况下，从子线程中获取登录数据是获取不到的，因为默认是 MODE_THREADLOCAL 策略。
存储策略在 System.getProperty("spring.security.strategy");加载，可以配置系统变量来修改策略。
在 VM option 参数添加
-Dspring.security.strategy=MODE_INHERITABLETHREADLOCAL
SpringContextHolder 默认将用户信息存储在 ThreadLocal 中，在 SpringBoot 中不同的请求使用不同的线程处理，是怎么获取到用户的信息的呢？ 下篇文章揭晓，有懂的可以在评论区留言。
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