超详细的逐句介绍Java反射之Field类和InvocationTargetException类函数源码讲解（全）
一、Field类和InvocationTargetException类
InvocationTargetException 是一个经过检查的异常，它包装了被调用的方法或构造函数抛出的异常。Field提供有关类或接口的单个字段的信息和动态访问。反射字段可以是类（静态）字段或实例字段。下面我将从源码角度详细介绍Field类和InvocationTargetException类内部源码
二、Field类源码介绍
Field类继承了AccessibleObject类，同时实现了接口Member
public final
class Field extends AccessibleObject implements Member {
}
下面定义了一些基本变量
private Class<?> clazz;
private int slot;
private String name;
private Class<?> type;
private int modifiers;
private transient String signature;
private transient FieldRepository genericInfo;
private byte[] annotations;
private FieldAccessor fieldAccessor;
private FieldAccessor overrideFieldAccessor;
private Field root;
获取泛型签名
private String getGenericSignature() {
return signature;}
获取泛型工厂
private GenericsFactory getFactory() {
Class<?> c = getDeclaringClass();
// create scope and factory
return CoreReflectionFactory.make(c, ClassScope.make(c));
}
获取字段存储库
private FieldRepository getGenericInfo() {
// lazily initialize repository if necessary
if (genericInfo == null) {
// create and cache generic info repository
genericInfo = FieldRepository.make(getGenericSignature(),
getFactory());
}
return genericInfo; //return cached repository
}
Field的构造方法
Field(Class<?> declaringClass,
String name,
Class<?> type,
int modifiers,
int slot,
String signature,
byte[] annotations)
{
this.clazz = declaringClass;
this.name = name;
this.type = type;
this.modifiers = modifiers;
this.slot = slot;
this.signature = signature;
this.annotations = annotations;
}
包私有例程（通过 ReflectAccess 暴露给 java.lang.Class）返回该字段的副本。 副本的“根”字段指向此字段。
Field copy() {
if (this.root != null)
throw new IllegalArgumentException("Can not copy a non-root Field");
Field res = new Field(clazz, name, type, modifiers, slot, signature, annotations);
res.root = this;
res.fieldAccessor = fieldAccessor;
res.overrideFieldAccessor = overrideFieldAccessor;
return res;
}
返回表示类或接口的 Class 对象，该类或接口声明了由此 Field 对象表示的字段
public Class<?> getDeclaringClass() {
return clazz;
}
获取字段名称
public String getName() {
return name;
}
获取修饰符
public int getModifiers() {
return modifiers;
}
判断是否是枚举
public boolean isEnumConstant() {
return (getModifiers() & Modifier.ENUM) != 0;
}
判断是否是合成字段
public boolean isSynthetic() {
return Modifier.isSynthetic(getModifiers());
}
定义获取类型
public Class<?> getType() {
return type;
}
获取泛型类型
public Type getGenericType() {
if (getGenericSignature() != null)
return getGenericInfo().getGenericType();
else
return getType();
}
将此Field与指定的对象进行比较
public boolean equals(Object obj) {
if (obj != null && obj instanceof Field) {
Field other = (Field)obj;
return (getDeclaringClass() == other.getDeclaringClass())
&& (getName() == other.getName())
&& (getType() == other.getType());
}
return false;
}
获取哈希值
public int hashCode() {
return getDeclaringClass().getName().hashCode() ^ getName().hashCode();
}
定义返回描述此Field的字符串
public String toString() {
int mod = getModifiers();
return (((mod == 0) ? "" : (Modifier.toString(mod) + " "))
+ getType().getTypeName() + " "
+ getDeclaringClass().getTypeName() + "."
+ getName());
}
转化为泛型字符串
public String toGenericString() {
int mod = getModifiers();
Type fieldType = getGenericType();
return (((mod == 0) ? "" : (Modifier.toString(mod) + " "))
+ fieldType.getTypeName() + " "
+ getDeclaringClass().getTypeName() + "."
+ getName());
}
在指定的对象上返回由此 Field 表示的字段的值。
public Object get(Object obj)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
return getFieldAccessor(obj).get(obj);
}
获取静态或实例布尔字段的值。
public boolean getBoolean(Object obj)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
return getFieldAccessor(obj).getBoolean(obj);
}
获取静态或实例字节字段的不同类型的值。
public byte getByte(Object obj)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
return getFieldAccessor(obj).getByte(obj);
}
public char getChar(Object obj)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
return getFieldAccessor(obj).getChar(obj);
}
public short getShort(Object obj)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
return getFieldAccessor(obj).getShort(obj);
}
public int getInt(Object obj)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
return getFieldAccessor(obj).getInt(obj);
}
public long getLong(Object obj)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
return getFieldAccessor(obj).getLong(obj);
}
public float getFloat(Object obj)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
return getFieldAccessor(obj).getFloat(obj);
}
public double getDouble(Object obj)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
return getFieldAccessor(obj).getDouble(obj);
}
设置某个对象的值。
public void set(Object obj, Object value)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
getFieldAccessor(obj).set(obj, value);
}
设置某个对象的布尔类型
public void setBoolean(Object obj, boolean z)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
getFieldAccessor(obj).setBoolean(obj, z);
}
设置某个对象的byte类型字
public void setByte(Object obj, byte b)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
getFieldAccessor(obj).setByte(obj, b);
}
设置某个对象的char类型字
public void setChar(Object obj, char c)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
getFieldAccessor(obj).setChar(obj, c);
}
设置某个对象的short类型字
public void setShort(Object obj, short s)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
getFieldAccessor(obj).setShort(obj, s);
}
设置某个对象的int类型字
public void setInt(Object obj, int i)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
getFieldAccessor(obj).setInt(obj, i);
}
设置某个对象的long类型字
public void setLong(Object obj, long l)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
getFieldAccessor(obj).setLong(obj, l);
}
设置某个对象的float类型字
public void setFloat(Object obj, float f)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
getFieldAccessor(obj).setFloat(obj, f);
}
设置某个对象的double类型字
public void setDouble(Object obj, double d)
throws IllegalArgumentException, IllegalAccessException
{
if (!override) {
if (!Reflection.quickCheckMemberAccess(clazz, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
checkAccess(caller, clazz, obj, modifiers);
}
}
getFieldAccessor(obj).setDouble(obj, d);
}
获取字段地址，中间为具体实现类，最后是对外接口类
private FieldAccessor getFieldAccessor(Object obj)
throws IllegalAccessException
{
boolean ov = override;
FieldAccessor a = (ov) ? overrideFieldAccessor : fieldAccessor;
return (a != null) ? a : acquireFieldAccessor(ov);
}
private FieldAccessor acquireFieldAccessor(boolean overrideFinalCheck) {
// First check to see if one has been created yet, and take it
// if so
FieldAccessor tmp = null;
if (root != null) tmp = root.getFieldAccessor(overrideFinalCheck);
if (tmp != null) {
if (overrideFinalCheck)
overrideFieldAccessor = tmp;
else
fieldAccessor = tmp;
} else {
// Otherwise fabricate one and propagate it up to the root
tmp = reflectionFactory.newFieldAccessor(this, overrideFinalCheck);
setFieldAccessor(tmp, overrideFinalCheck);
}
return tmp;
}
private FieldAccessor getFieldAccessor(boolean overrideFinalCheck) {
return (overrideFinalCheck)? overrideFieldAccessor : fieldAccessor;
}
设置字段地址
private void setFieldAccessor(FieldAccessor accessor, boolean overrideFinalCheck) {
if (overrideFinalCheck)
overrideFieldAccessor = accessor;
else
fieldAccessor = accessor;
// Propagate up
if (root != null) {
root.setFieldAccessor(accessor, overrideFinalCheck);
}
}
定于注解类型
public <T extends Annotation> T getAnnotation(Class<T> annotationClass) {
Objects.requireNonNull(annotationClass);
return annotationClass.cast(declaredAnnotations().get(annotationClass));
}
定义获取注解类型
public <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass) {
Objects.requireNonNull(annotationClass);
return AnnotationSupport.getDirectlyAndIndirectlyPresent(declaredAnnotations(), annotationClass);
}
返回直接出现在此元素上的注释## 三、InvocationTargetException类源码介绍
InvocationTargetException类
public Annotation[] getDeclaredAnnotations() {
return AnnotationParser.toArray(declaredAnnotations());
}
定义注解泛型和注解键值对
private transient Map<Class<? extends Annotation>, Annotation> declaredAnnotations;
生成泛型-注解键值对
private synchronized Map<Class<? extends Annotation>, Annotation> declaredAnnotations() {
if (declaredAnnotations == null) {
Field root = this.root;
if (root != null) {
declaredAnnotations = root.declaredAnnotations();
} else {
declaredAnnotations = AnnotationParser.parseAnnotations(
annotations,
sun.misc.SharedSecrets.getJavaLangAccess().getConstantPool(getDeclaringClass()),
getDeclaringClass());
}
}
return declaredAnnotations;
}
调用JVM获取注解byte数组
private native byte[] getTypeAnnotationBytes0();
定义获取注解类型对外接口类
public AnnotatedType getAnnotatedType() {
return TypeAnnotationParser.buildAnnotatedType(getTypeAnnotationBytes0(),
sun.misc.SharedSecrets.getJavaLangAccess().
getConstantPool(getDeclaringClass()),
this,
getDeclaringClass(),
getGenericType(),
TypeAnnotation.TypeAnnotationTarget.FIELD);
}
三、InvocationTargetException类
InvocationTargetException类继承了ReflectiveOperationException类
public class InvocationTargetException extends ReflectiveOperationException {
}
下面定义了通用串行ID
private static final long serialVersionUID = 4085088731926701167L;
返回目标
private Throwable target;
构造一个以 null 作为目标异常的 InvocationTargetException。
protected InvocationTargetException() {
super((Throwable)null);
构造一个带有目标异常的 InvocationTargetException。
public InvocationTargetException(Throwable target) {
super((Throwable)null); // Disallow initCause
this.target = target;
}
构造一个带有目标异常和详细消息的 InvocationTargetException
public InvocationTargetException(Throwable target, String s) {
super(s, null); // Disallow initCause
this.target = target;
}
获取抛出的目标异常
public Throwable getTargetException() {
return target;
}
返回此异常的原因（抛出的目标异常，可能为null
public Throwable getCause() {
return target;
}