Spring笔记

2023-08-24 23:49| 来源: 网络整理| 查看: 265

前面2篇作为铺垫

对java-Type的理解 java-Type的获取方式

之前讲过Class，Field，Method都有获取Type的需求,ResolvableType就是一个抽象的结果

1. 构建ResolvableType对象

ResolvableType提供了静态for方法进行构建,下面我们以代码来示例

1.1.forClass @SuppressWarnings("serial") static class ExtendsList extends ArrayList { } @Test public void forClass() throws Exception { ResolvableType type = ResolvableType.forClass(ExtendsList.class); assertThat(type.getType(), equalTo((Type) ExtendsList.class)); } 1.2.forField @Test public void forField() throws Exception { Field field = Fields.class.getField("charSequenceList"); ResolvableType type = ResolvableType.forField(field); assertThat(type.getType(), equalTo(field.getGenericType())); } 1.3 forMethodParameter

forMethodParameter还有很多变种 1.3.1 forConstructorParameter 1.3.2 forMethodReturnType

@Test public void forMethodParameter() throws Exception { Method method = Methods.class.getMethod("charSequenceParameter", List.class); MethodParameter methodParameter = MethodParameter.forMethodOrConstructor(method, 0); ResolvableType type = ResolvableType.forMethodParameter(methodParameter); assertThat(type.getType(), equalTo(method.getGenericParameterTypes()[0])); } 2.1 getType方法

获取自身类型

@Test public void forClassTest() throws Exception { ResolvableType type = ResolvableType.forClass(ExtendsList.class); assertThat(type.getType(), equalTo((Type) ExtendsList.class)); assertThat(type.getRawClass(), equalTo(ExtendsList.class)); } 2.2 getSuperType方法 @Test public void superTypeTest() throws Exception { ResolvableType type = ResolvableType.forType(ExtendsList.class); ResolvableType superType=type.getSuperType(); System.out.println(superType.getType()); }

输出结果:

java.util.ArrayList 2.3 getRawClass

当Type为ParameterizedType时有效

@Test public void getRawClassTest() throws Exception { ResolvableType type = ResolvableType.forType(ExtendsList.class); ResolvableType superType=type.getSuperType(); System.out.println(superType.getRawClass()); }

输出结果:

java.util.ArrayList 2.4 as方法

上面的方式可以将ExtendsList以as的方式转换一下,向上取接口或父类

@Test public void asTest() throws Exception { ResolvableType type = ResolvableType.forType(ExtendsList.class); ResolvableType listType=type.as(ArrayList.class); System.out.println(listType.getType()); System.out.println(listType.getRawClass()); }

输出结果:

java.util.ArrayList class java.util.ArrayList 2.5 getGeneric方法

这时候看起来使用应该是比较简单了

@Test public void getGenericTest() throws Exception { ResolvableType type = ResolvableType.forType(ExtendsList.class); ResolvableType listType=type.as(ArrayList.class); System.out.println(listType.getGeneric().getType()); } 2.6 resolveGeneric方法

更加简化的一种方法

@Test public void resolveGenericTest() throws Exception { ResolvableType type = ResolvableType.forType(ExtendsList.class); ResolvableType listType=type.as(ArrayList.class); System.out.println(listType.resolveGeneric()); } 2.7 getComponentType方法

返回数组类型

@Test public void getComponentTypeForClassArray() throws Exception { Field field = Fields.class.getField("arrayClassType"); ResolvableType type = ResolvableType.forField(field); assertThat(type.isArray(), equalTo(true)); assertThat(type.getComponentType().getType(), equalTo((Type) ((Class) field.getGenericType()).getComponentType())); } @Test public void getComponentTypeForGenericArrayType() throws Exception { ResolvableType type = ResolvableType.forField(Fields.class.getField("genericArrayType")); assertThat(type.isArray(), equalTo(true)); assertThat(type.getComponentType().getType(), equalTo(((GenericArrayType) type.getType()).getGenericComponentType())); }

参考: http://jinnianshilongnian.iteye.com/blog/1993608

【本文地址】

公司简介

联系我们