getField()与getDeclaredField()的区别

Java的反射机制中，用Class的getField(String name)或getDelaredField(String name)可以得到目标类的指定属性，返回类型是Field。

在看它们的区别之前先看下它们的源码(英文部分自己翻译了下)：

/*** Returns a {@code Field} object that reflects the specified public member* field of the class or interface represented by this {@code Class}* object. The {@code name} parameter is a {@code String} specifying the* simple name of the desired field.** 返回一个域对象，反射出这个类对象所代表的类或接口的指定的Public 域成员。* 名称参数是由字符串所指定的期望域的简单名称* 
 The field to be reflected is determined by the algorithm that* follows.  Let C be the class or interface represented by this object:*  *  这个域被如下的算法所决定。C是这个对象所代表的类或者接口* 
* 
 If C declares a public field with the name specified, that is the*      field to be reflected.
*  如果C声明一个由指定名称的公共域，那就是要被反射的域* 
 If no field was found in step 1 above, this algorithm is applied*      recursively to each direct superinterface of C. The direct*      superinterfaces are searched in the order they were declared.
* 如果在步骤1中没有域被找到，这个算法将递归应用到每个C的父接口中。直接的父接口* 将由声明顺序遍历查找。* 
 If no field was found in steps 1 and 2 above, and C has a*      superclass S, then this algorithm is invoked recursively upon S.*      If C has no superclass, then a {@code NoSuchFieldException}*      is thrown.
* 
* 如果在步骤1和步骤2中，没有域被找到，C有一个父类型S，然后这个算法将被在S上递归调用。* 如果C没有父类，则会抛出NoSuchFieldException的异常* 
 If this {@code Class} object represents an array type, then this* method does not find the {@code length} field of the array type.** 如果这个类对象代表一个数组类型，那么这个方法将找不到这个数组类型的length域* @param name the field name* @return the {@code Field} object of this class specified by*         {@code name}* @throws NoSuchFieldException if a field with the specified name is*         not found.* @throws NullPointerException if {@code name} is {@code null}* @throws SecurityException*         If a security manager, s, is present and*         the caller's class loader is not the same as or an*         ancestor of the class loader for the current class and*         invocation of {@link SecurityManager#checkPackageAccess*         s.checkPackageAccess()} denies access to the package*         of this class.** @since JDK1.1* @jls 8.2 Class Members* @jls 8.3 Field Declarations*/@CallerSensitivepublic Field getField(String name)throws NoSuchFieldException, SecurityException {checkMemberAccess(Member.PUBLIC, Reflection.getCallerClass(), true);Field field = getField0(name);if (field == null) {throw new NoSuchFieldException(name);}return field;}

/*** Returns a {@code Field} object that reflects the specified declared* field of the class or interface represented by this {@code Class}* object. The {@code name} parameter is a {@code String} that specifies* the simple name of the desired field.* *返回一个域对象，反射出这个类对象所代表的类或接口所声明的所有域成员。* 名称参数是由字符串所指定的期望域的简单名称* 
 If this {@code Class} object represents an array type, then this* method does not find the {@code length} field of the array type.* *如果这个类对象代表一个数组类型，那么这个方法将找不到这个数组类型的length域* @param name the name of the field* @return  the {@code Field} object for the specified field in this*          class* @throws  NoSuchFieldException if a field with the specified name is*          not found.* @throws  NullPointerException if {@code name} is {@code null}* @throws  SecurityException*          If a security manager, s, is present and any of the*          following conditions is met:**          
**          
 the caller's class loader is not the same as the*          class loader of this class and invocation of*          {@link SecurityManager#checkPermission*          s.checkPermission} method with*          {@code RuntimePermission("accessDeclaredMembers")}*          denies access to the declared field**          
 the caller's class loader is not the same as or an*          ancestor of the class loader for the current class and*          invocation of {@link SecurityManager#checkPackageAccess*          s.checkPackageAccess()} denies access to the package*          of this class**          
** @since JDK1.1* @jls 8.2 Class Members* @jls 8.3 Field Declarations*/@CallerSensitivepublic Field getDeclaredField(String name)throws NoSuchFieldException, SecurityException {checkMemberAccess(Member.DECLARED, Reflection.getCallerClass(), true);Field field = searchFields(privateGetDeclaredFields(false), name);if (field == null) {throw new NoSuchFieldException(name);}return field;}

getField(String name)只能获取public的字段，包括父类的；

而getDeclaredField(String name)能获取自己声明的各种字段，包括public，protected，private。

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