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_nami/nami/src/main/java/org/noear/nami/common/MethodHandlesUtil.java
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| package org.noear.nami.common; | ||
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| import java.lang.invoke.MethodHandle; | ||
| import java.lang.invoke.MethodHandles; | ||
| import java.lang.reflect.Constructor; | ||
| import java.lang.reflect.InvocationTargetException; | ||
| import java.lang.reflect.Method; | ||
|
|
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| /** | ||
| * jdk8中如果直接调用{@link MethodHandles#lookup()}获取到的{@link MethodHandles.Lookup} | ||
| * <p> | ||
| * 在调用方法 {@link MethodHandles.Lookup#findSpecial(java.lang.Class, java.lang.String, java.lang.invoke.MethodType, java.lang.Class)} | ||
| * <p> | ||
| * 和{@link MethodHandles.Lookup#unreflectSpecial(java.lang.reflect.Method, java.lang.Class)} | ||
| * 获取父类方法句柄{@link MethodHandle}时 | ||
| * <p> | ||
| * 可能出现权限不够, 抛出如下异常, 所以通过反射创建{@link MethodHandles.Lookup}解决该问题. | ||
| * <pre> | ||
| * java.lang.IllegalAccessException: no private access for invokespecial: interface com.example.demo.methodhandle.UserService, from com.example.demo.methodhandle.UserServiceInvoke | ||
| * at java.lang.invoke.MemberName.makeAccessException(MemberName.java:850) | ||
| * at java.lang.invoke.MethodHandles$Lookup.checkSpecialCaller(MethodHandles.java:1572) | ||
| * </pre> | ||
| * <p> | ||
| * 而jdk11中直接调用{@link MethodHandles#lookup()}获取到的{@link MethodHandles.Lookup},也只能对接口类型才会权限获取方法的方法句柄{@link MethodHandle}. | ||
| * <p> | ||
| * 如果是普通类型Class,需要使用jdk9开始提供的 MethodHandles#privateLookupIn(java.lang.Class, java.lang.invoke.MethodHandles.Lookup)方法. | ||
| */ | ||
| public class MethodHandlesUtil { | ||
| private static final int ALLOWED_MODES = MethodHandles.Lookup.PRIVATE | MethodHandles.Lookup.PROTECTED | ||
| | MethodHandles.Lookup.PACKAGE | MethodHandles.Lookup.PUBLIC; | ||
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| private static Constructor<MethodHandles.Lookup> java8LookupConstructor; | ||
| private static Method privateLookupInMethod; | ||
|
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| static { | ||
| //先查询jdk9 开始提供的java.lang.invoke.MethodHandles.privateLookupIn方法, | ||
| //如果没有说明是jdk8的版本.(不考虑jdk8以下版本) | ||
| try { | ||
| privateLookupInMethod = MethodHandles.class.getMethod("privateLookupIn", Class.class, MethodHandles.Lookup.class); | ||
| } catch (NoSuchMethodException e) { | ||
| privateLookupInMethod = null; | ||
| System.out.println("There is no [java.lang.invoke.MethodHandles.privateLookupIn(Class, Lookup)] method in this version of JDK"); | ||
| } | ||
| //jdk8 | ||
| //这种方式其实也适用于jdk9及以上的版本,但是上面优先,可以避免 jdk9 反射警告 | ||
| if (privateLookupInMethod == null) { | ||
| try { | ||
| java8LookupConstructor = MethodHandles.Lookup.class.getDeclaredConstructor(Class.class, int.class); | ||
| java8LookupConstructor.setAccessible(true); | ||
| } catch (NoSuchMethodException e) { | ||
| //可能是jdk8 以下版本 | ||
| throw new IllegalStateException( | ||
| "There is neither 'privateLookupIn(Class, Lookup)' nor 'Lookup(Class, int)' method in java.lang.invoke.MethodHandles.", | ||
| e); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| /** | ||
| * java9中的MethodHandles.lookup()方法返回的Lookup对象 | ||
| * 有权限访问specialCaller != lookupClass()的类 | ||
| * 但是只能适用于接口, {@link java.lang.invoke.MethodHandles.Lookup#checkSpecialCaller} | ||
| */ | ||
| public static MethodHandles.Lookup lookup(Class<?> callerClass) { | ||
| //使用反射,因为当前jdk可能不是java9或以上版本 | ||
| if (privateLookupInMethod != null) { | ||
| try { | ||
| return (MethodHandles.Lookup) privateLookupInMethod.invoke(MethodHandles.class, callerClass, MethodHandles.lookup()); | ||
| } catch (IllegalAccessException | InvocationTargetException e) { | ||
| throw new RuntimeException(e); | ||
| } | ||
| } | ||
| //jdk 8 | ||
| try { | ||
| return java8LookupConstructor.newInstance(callerClass, ALLOWED_MODES); | ||
| } catch (Exception e) { | ||
| throw new IllegalStateException("no 'Lookup(Class, int)' method in java.lang.invoke.MethodHandles.", e); | ||
| } | ||
| } | ||
|
|
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| public static MethodHandle getSpecialMethodHandle(Method parentMethod) { | ||
| final Class<?> declaringClass = parentMethod.getDeclaringClass(); | ||
| MethodHandles.Lookup lookup = lookup(declaringClass); | ||
| try { | ||
| return lookup.unreflectSpecial(parentMethod, declaringClass); | ||
| } catch (IllegalAccessException e) { | ||
| throw new RuntimeException(e); | ||
| } | ||
| } | ||
| } |