Java Reflection API with Example

Safalta Expert Published by: Aryan Rana Updated Sat, 03 Dec 2022 09:39 AM IST

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In this article, we'll talk about Java reflection. Here, we'll examine what Java Reflection is and how it works to obtain data. We will also consider the advantages and disadvantages of Java's reflection. In addition, we will comprehend a Java reflection class and some sample code that uses reflection. Invoking a method using Java reflection will allow us to see the Java reflection in action.

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Table of Content
What does "Java reflection" mean?
How Does Java Reflection Collect Data?

Source: Safalta

lang. reflect Package">Class in java. lang. reflect Package

Java. lang.methods Class's
Java Reflection's advantages and disadvantages
Examples of Java Reflections
 

What does "Java reflection" mean?

Application Programming Interface (API) reflection in Java is used at runtime to change classes, methods, and interfaces. It is also used to examine or modify the behaviour of methods, classes, and interfaces while they are in use. Reflection provides information about the class that an object belongs to as well as the methods for that class that use the object in their execution. Reflection allows us to invoke methods at runtime regardless of the access specifiers used with them.
 

How Does Java Reflection Collect Data?

Reflection can be used to obtain information about -

Class: To find the name of the class that an object belongs to, use the getClass() method.

Constructors: The public constructors of the class that an object belongs to can be obtained using the getConstructors() method.

Strategies: The public methods for the class that an object belongs to can be obtained using the get methods() method.

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Class in java. lang. reflect Package

The list of different Java classes in the java.lang.package to implement reflection is as follows:

Field: This class is used to collect declarative data, such as a variable's name, value, datatype, and access modifier.

Method: This class is used to collect declarative information about a method, including its name, return type, access modifier, parameter types, and exception type.

Constructor: This class is used to collect declarative information about a constructor, such as a name, access modifier, and parameter types.

Modifier: To learn more about a specific access modifier, use this class.
 

Java. lang.methods Class's

  • The class name is returned by the public-str getName function.
  • The superclass reference is returned by the public method getSuperclass().
  • Private Class, An array of interfaces implemented by the specified class is returned by the getInterfaces() method.
  • Public static String to String (int I method), which returns the access specifier for the specified class, requires a parameter called "public static String to String ()" to be passed as it returns an integer value representing the modifiers of the specified class.

 

Java Reflection's advantages and disadvantages

Advantages of Java Reflection- 

  • Extensibility Features: An application can use outer, user-defined classes by creating extensibility objects using examples of those classes' fully qualified names.
  • Device debugging and testing: Debuggers use the reflection property to look at individual students in classes.
 

Disadvantages of Java's Reflection-

  • Execution Time: Reflective tasks take longer to complete.
  • Internals: Reflective code disrupts thought processes.

 

Examples of Java Reflections-

Example 1: How to obtain class metadata

How to obtain class-specific metadata, such as the class's name, superclass name, implemented interfaces, and access modifiers.

Name of the class-

Its access modifiers are-

It has implemented interfaces-

Its superclass is-
 

Example 2: How to obtain variable metadata

Make a class object for the aforementioned class.

Obtain the metadata as a field array.

Use the "public String getName()" method to retrieve the variable names.

Utilize the "public Class getType()" method to determine the data type of the variables.

Use the "publicget (Field)" method to retrieve the value of the variable.

 

Example 3: How to obtain a method's metadata

Make the class object for the aforementioned class.

Obtain method details in a Method array.

Utilize the getName() method to obtain the method's name.

Utilize the getReturnType() method to determine the method's return type.

Get the method access modifiers.

The getParameterTypes method, which returns a class array, can be used to obtain method parameter types.
 

Example 4: How to obtain constructors' metadata

a class object was created for-

Compiled all the constructors' metadata into a constructor array.

All of the constructor access modifiers were printed in-

Printed constructor parameter types in-

Constructors throw printed exceptions when-

Consequently, we have a thorough understanding of Java reflection. In addition, we covered an introduction to reflection in Java in this tutorial. Along with this, Java Reflection's benefits and drawbacks were demonstrated. Finally, with the aid of examples, we learned about the Java reflection class and how Java reflection invokes a method.

What is accurate regarding Java reflection and API?

Java Reflection is a process for looking at or changing a class's run-time behavior. A class's run-time behavior can be examined and changed using a variety of methods provided by java. lang. Class class.

Is Java reflection effective in terms of speed?

Reflective operations, as a result of their slower performance compared to their non-reflective counterparts, should be avoided in code segments that are frequently called in performance-sensitive applications.

Why reflection is expensive?

Reflection needs to load and then process a significant amount of the type metadata. As a result, there may be more memory overhead and slower processing.

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