在Java中通过Reflection设置私有字段的最短，最佳，最干净的方法是什么? [英] What is the shortest, best, cleanest way to set a private field via Reflection in Java?

问题描述

我已经在Java中使用过Reflection.但是，如果您使用的是Java标准(例如，注入私有字段)，则必须编写大量代码才能完成工作.

在Java对象中注入私有字段的最短方法是什么?广泛使用且可用于生产环境的库中是否有实现?

解决方案

一线"

  FieldUtils.writeField(对象目标，字符串fieldName，对象值，布尔值ForceAccess) 

如果您的项目使用 Apache Commons Lang 通过反射设置值的最短方法是在类'org.apache.commons.lang3.reflect.FieldUtils' 中使用静态方法'writeField'>

下面的简单示例显示了带有字段PaymentService的Bookstore-Object.该代码显示了如何使用不同的值两次设置私有字段.

  import org.apache.commons.lang3.reflect.FieldUtils;公共类Main2 {公共静态void main(String [] args)抛出IllegalAccessException {书店书店= new Bookstore();//只需一行就可以通过反射注入场FieldUtils.writeField(bookstore，"paymentService"，new Paypal()，true)；bookstore.pay();//印刷品:付款人:Paypal//只需一行就可以通过反射注入场FieldUtils.writeField(bookstore，"paymentService"，new Visa()，true)；bookstore.pay();//支付方式:Visa}公共静态类Paypal实现了PaymentService {}公共静态类Visa实现了PaymentService {}公共静态类书店{私人PaymentService PaymentService;无效的公共薪酬(){System.out.println(付款人:" + this.paymentService.getClass().getSimpleName());}}} 

您可以通过Maven Central获得lib:

 < dependency>< groupId> org.apache.commons</groupId>< artifactId> commons-lang3</artifactId>< version> 3.8.1</version></dependency> 

Hi I've already worked with Reflection in Java. But if you are using the java standards (e.g. injecting a private field) you have to write a lot of code to get the job done.

What is the shortest way to inject a private field in a Java Object? Are there implementations in widely used and production ready libraries?

解决方案

The "One-Liner"

FieldUtils.writeField(Object target, String fieldName, Object value, boolean forceAccess)

If your Project uses Apache Commons Lang the shortest way to set a value via reflection is to use the static Method 'writeField' in the class 'org.apache.commons.lang3.reflect.FieldUtils'

The following simple example shows a Bookstore-Object with a field paymentService. The code shows how the private field is set two times with a different value.

import org.apache.commons.lang3.reflect.FieldUtils;

public class Main2 {
    public static void main(String[] args) throws IllegalAccessException {
        Bookstore bookstore = new Bookstore();

        //Just one line to inject the field via reflection
        FieldUtils.writeField(bookstore, "paymentService",new Paypal(), true);
        bookstore.pay(); // Prints: Paying with: Paypal

        //Just one line to inject the field via reflection
        FieldUtils.writeField(bookstore, "paymentService",new Visa(), true);
        bookstore.pay();// Prints Paying with: Visa
    }

    public static class Paypal implements  PaymentService{}

    public static class Visa implements  PaymentService{}

    public static class Bookstore {
        private  PaymentService paymentService;
        public void pay(){
            System.out.println("Paying with: "+ this.paymentService.getClass().getSimpleName());
        }
    }
}

You can get the lib via maven central:

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.8.1</version>
</dependency>

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