![]() ![]() "Since reflection allows code to perform operations that would be illegal in non-reflective code, such as accessing private fields and methods, the use of reflection can result in unexpected side-effects, which may render code dysfunctional and may destroy portability. But as per the Oracle documentation in the section drawbacks they recommended that : Using the Reflection in Java you can access all the private/public fields and methods of one class to another. The RuntimeExceptions which may be thrown are either SecurityExceptions (if the JVM's SecurityManager will not allow you to change a field's accessibility), or IllegalArgumentExceptions, if you try and access the field on an object not of the field's class's type: f.get("BOB") //will throw IllegalArgumentException, as String is of the wrong type The IllegalAccessException would be thrown if the field was not accessible (for example, if it is private and has not been made accessible via missing out the f.setAccessible(true) line. obj.getClass().getDeclaredField("misspelled") //will throw NoSuchFieldException The NoSuchFieldException would be thrown if you asked for a field by a name which did not correspond to a declared field. Hashtable iWantThis = (Hashtable) f.get(obj) //IllegalAccessExceptionĮDIT: as has been commented by aperkins, both accessing the field, setting it as accessible and retrieving the value can throw Exceptions, although the only checked exceptions you need to be mindful of are commented above. We know that private fields and methods can’t be accessible outside of the class but using reflection we can get/set the private field value by turning off the java access check for field modifiers. Let me know if you have any questions, I’d be happy to help if I can.In order to access private fields, you need to get them from the class's declared fields and then make them accessible: Field f = obj.getClass().getDeclaredField("stuffIWant") //NoSuchFieldException In summary, steps 2, 3, and 4 are three lines of code using Spring’s ReflectionUtils to reflectively set a value on an object. ![]() another objects private fields), although those privileges can be. This method takes three arguments, the Field reference, the object to set the value on, and the value to set. Reflection lets Java code look at an object (more precisely, the class of the object). This step uses the Spring tField method to set the value on the object. Using reflection, set the value on the object. This method takes one argument, the Field reference. This step uses the Spring ReflectionUtils.makeAccessible method. The accessible flag toggles reflection access to Java internals, such as fields. Using reflection, set the field’s accessible flag to true so we can then set the field’s value. Field field = ReflectionUtils.findField(MyEntity.class, "createDate") ģ. This method takes two arguments, the Class having the field and the name of the field. This step uses the Spring ReflectionUtils.findField method. Using reflection, obtain the Field reference from the class with the field to set. LocalDateTime value = LocalDateTime.now() Ģ. In this example, “object” needs the “value” (no reflection in use in this step!). Identify the object to set the value on (the one without the setter) and the value to set. The following steps show how to use it.ġ. The Spring ReflectionUtils class makes this a little easier. While directly using reflection for this is not difficult, it has some extra steps and checked exceptions to handle. This approach usually involves using Java’s reflection. When a production code field should not have a setter method, typically in an immutable domain model, we need to use a different approach in tests for giving that field a value in an existing instance. Here is a quick tip I recently shared with my team that I thought you might find useful. We also hope to share these quick tips with you in hopes it will help you someday in your work. ![]() Whether it’s someone on our team at that moment or a colleague working on another project, we make it a point to collaboratively share information to move all projects and clients forward. We’ll often post updates on certain contributions here on our blog to keep our readers in the know.Īt Intertech we do a lot of sharing of expertise. Non-reflection code perspective about some operation like accessing the private fields are illegal, so Java Reflections implementation of such operation. That means we’re often active members on sites and forums such as GitHub, Stack Overflow, and many other developer resource sites. At Intertech we believe strongly in contributing to and advancing the developer community. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |