Java get method with annotation

Method Class | getParameterAnnotations() method in Java

The java.lang.reflect.Method.getParameterAnnotations() method of Method class returns a two-dimensional Annotation array, that represents the annotations on the parameters, of the Method object. If the Method contains no parameters, an empty array will be returned. If the Method contains one or more parameters then a two-dimension Annotation array will be returned. A nested array of this two-dimension array will be empty for the parameter with no annotations. At the time of compilation mandated and synthetic parameters are added to the array. Mandated parameter are parameters which implicitly declared in source and Synthetic parameter are parameters that are neither implicitly nor explicitly declared in the source. The objects of annotation returned by this method are serializable. The array of arrays returned by this method can be easily modified.

public Annotation[][] getParameterAnnotations()

Return Value: This method returns a two-dimensional Annotation array, that represent the annotations on the formal and implicit parameters, of the Method object. Below programs illustrates getParameterAnnotations() method of Method class:

Example 1: To use getParameterAnnotations() for a Specific Method given as Input. The program contains a Method name setManyValues() which contains parameter Annotations. So this program is going to get all parameter Annotations contain by setManyValues() Method.

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Java get method with annotation

A Method provides information about, and access to, a single method on a class or interface. The reflected method may be a class method or an instance method (including an abstract method). A Method permits widening conversions to occur when matching the actual parameters to invoke with the underlying method’s formal parameters, but it throws an IllegalArgumentException if a narrowing conversion would occur.

Field Summary

Fields inherited from interface java.lang.reflect.Member

Method Summary

Returns an AnnotatedType object that represents the use of a type to specify the return type of the method/constructor represented by this Executable.

Returns this element’s annotation for the specified type if such an annotation is present, else null.

Returns the Class object representing the class or interface that declares the executable represented by this object.

Returns an array of Class objects that represent the types of exceptions declared to be thrown by the underlying executable represented by this object.

Returns an array of Type objects that represent the exceptions declared to be thrown by this executable object.

Returns an array of Type objects that represent the formal parameter types, in declaration order, of the executable represented by this object.

Returns a Type object that represents the formal return type of the method represented by this Method object.

Returns an array of arrays of Annotation s that represent the annotations on the formal parameters, in declaration order, of the Executable represented by this object.

Returns the number of formal parameters (whether explicitly declared or implicitly declared or neither) for the executable represented by this object.

Returns an array of Class objects that represent the formal parameter types, in declaration order, of the executable represented by this object.

Returns a Class object that represents the formal return type of the method represented by this Method object.

Returns an array of TypeVariable objects that represent the type variables declared by the generic declaration represented by this GenericDeclaration object, in declaration order.

Invokes the underlying method represented by this Method object, on the specified object with the specified parameters.

Returns true if this executable was declared to take a variable number of arguments; returns false otherwise.

Methods inherited from class java.lang.reflect.Executable

Methods inherited from class java.lang.reflect.AccessibleObject

Methods inherited from class java.lang.Object

Methods inherited from interface java.lang.reflect.AnnotatedElement

Method Detail

getDeclaringClass

Returns the Class object representing the class or interface that declares the executable represented by this object.

getName

getModifiers

getTypeParameters

Returns an array of TypeVariable objects that represent the type variables declared by the generic declaration represented by this GenericDeclaration object, in declaration order. Returns an array of length 0 if the underlying generic declaration declares no type variables.

getReturnType

Returns a Class object that represents the formal return type of the method represented by this Method object.

getGenericReturnType

Returns a Type object that represents the formal return type of the method represented by this Method object. If the return type is a parameterized type, the Type object returned must accurately reflect the actual type parameters used in the source code. If the return type is a type variable or a parameterized type, it is created. Otherwise, it is resolved.

getParameterTypes

Returns an array of Class objects that represent the formal parameter types, in declaration order, of the executable represented by this object. Returns an array of length 0 if the underlying executable takes no parameters.

getParameterCount

public int getParameterCount()

Returns the number of formal parameters (whether explicitly declared or implicitly declared or neither) for the executable represented by this object.

getGenericParameterTypes

Returns an array of Type objects that represent the formal parameter types, in declaration order, of the executable represented by this object. Returns an array of length 0 if the underlying executable takes no parameters. If a formal parameter type is a parameterized type, the Type object returned for it must accurately reflect the actual type parameters used in the source code. If a formal parameter type is a type variable or a parameterized type, it is created. Otherwise, it is resolved.

getExceptionTypes

Returns an array of Class objects that represent the types of exceptions declared to be thrown by the underlying executable represented by this object. Returns an array of length 0 if the executable declares no exceptions in its throws clause.

getGenericExceptionTypes

Returns an array of Type objects that represent the exceptions declared to be thrown by this executable object. Returns an array of length 0 if the underlying executable declares no exceptions in its throws clause. If an exception type is a type variable or a parameterized type, it is created. Otherwise, it is resolved.

equals

Compares this Method against the specified object. Returns true if the objects are the same. Two Methods are the same if they were declared by the same class and have the same name and formal parameter types and return type.

hashCode

Returns a hashcode for this Method . The hashcode is computed as the exclusive-or of the hashcodes for the underlying method’s declaring class name and the method’s name.

toString

Returns a string describing this Method . The string is formatted as the method access modifiers, if any, followed by the method return type, followed by a space, followed by the class declaring the method, followed by a period, followed by the method name, followed by a parenthesized, comma-separated list of the method’s formal parameter types. If the method throws checked exceptions, the parameter list is followed by a space, followed by the word throws followed by a comma-separated list of the thrown exception types. For example:

public boolean java.lang.Object.equals(java.lang.Object)

The access modifiers are placed in canonical order as specified by «The Java Language Specification». This is public , protected or private first, and then other modifiers in the following order: abstract , default , static , final , synchronized , native , strictfp .

toGenericString

Returns a string describing this Method , including type parameters. The string is formatted as the method access modifiers, if any, followed by an angle-bracketed comma-separated list of the method’s type parameters, if any, followed by the method’s generic return type, followed by a space, followed by the class declaring the method, followed by a period, followed by the method name, followed by a parenthesized, comma-separated list of the method’s generic formal parameter types. If this method was declared to take a variable number of arguments, instead of denoting the last parameter as «Type[]«, it is denoted as «Type. «. A space is used to separate access modifiers from one another and from the type parameters or return type. If there are no type parameters, the type parameter list is elided; if the type parameter list is present, a space separates the list from the class name. If the method is declared to throw exceptions, the parameter list is followed by a space, followed by the word throws followed by a comma-separated list of the generic thrown exception types. The access modifiers are placed in canonical order as specified by «The Java Language Specification». This is public , protected or private first, and then other modifiers in the following order: abstract , default , static , final , synchronized , native , strictfp .

invoke

public Object invoke(Object obj, Object. args) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException

Invokes the underlying method represented by this Method object, on the specified object with the specified parameters. Individual parameters are automatically unwrapped to match primitive formal parameters, and both primitive and reference parameters are subject to method invocation conversions as necessary. If the underlying method is static, then the specified obj argument is ignored. It may be null. If the number of formal parameters required by the underlying method is 0, the supplied args array may be of length 0 or null. If the underlying method is an instance method, it is invoked using dynamic method lookup as documented in The Java Language Specification, Second Edition, section 15.12.4.4; in particular, overriding based on the runtime type of the target object will occur. If the underlying method is static, the class that declared the method is initialized if it has not already been initialized. If the method completes normally, the value it returns is returned to the caller of invoke; if the value has a primitive type, it is first appropriately wrapped in an object. However, if the value has the type of an array of a primitive type, the elements of the array are not wrapped in objects; in other words, an array of primitive type is returned. If the underlying method return type is void, the invocation returns null.

isBridge

isVarArgs

Returns true if this executable was declared to take a variable number of arguments; returns false otherwise.

Источник

java.lang.reflect.Method.getAnnotation() Method Example

The java.lang.reflect.Method.getAnnotation(Class annotationClass) method returns this element’s annotation for the specified type if such an annotation is present, else null.

Declaration

Following is the declaration for java.lang.reflect.Method.getAnnotation(Class annotationClass) method.

public T getAnnotation(Class annotationClass)

Parameters

annotationClass − the Class object corresponding to the annotation type.

Returns

this element’s annotation for the specified annotation type if present on this element, else null.

Exceptions

NullPointerException − if the given annotation class is null.

Example

The following example shows the usage of java.lang.reflect.Method.getAnnotation(Class annotationClass) method.

package com.tutorialspoint; import java.lang.annotation.Annotation; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.reflect.Method; public class MethodDemo < public static void main(String[] args) < Method[] methods = SampleClass.class.getMethods(); Annotation annotation = methods[0].getAnnotation(CustomAnnotation.class); if(annotation instanceof CustomAnnotation)< CustomAnnotation customAnnotation = (CustomAnnotation) annotation; System.out.println("name: " + customAnnotation.name()); System.out.println("value: " + customAnnotation.value()); >> > @CustomAnnotation(name = «SampleClass», value = «Sample Class Annotation») class SampleClass < private String sampleField; @CustomAnnotation(name="getSampleMethod", value = "Sample Method Annotation") public String getSampleField() < return sampleField; >public void setSampleField(String sampleField) < this.sampleField = sampleField; >> @Retention(RetentionPolicy.RUNTIME) @interface CustomAnnotation

Let us compile and run the above program, this will produce the following result −

name: getSampleMethod value: Sample Method Annotation

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