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大家知道ASM可以来分析 修改类 从前学习spring的时候里面有个叫IOC的技术,不知道他的底层实现感觉很神秘,
我们提供的服务有:成都网站制作、做网站、微信公众号开发、网站优化、网站认证、赣州ssl等。为上1000+企事业单位解决了网站和推广的问题。提供周到的售前咨询和贴心的售后服务,是有科学管理、有技术的赣州网站制作公司但是最近在看ASM的东西,感觉结合反射用它就可以实现自动注入的功能。例子如下
那spring里面是如何实现的呢?
// 注解类 package hgs.asm; public @interface AutoWare { } //AnoDesc 里面的一个属性 package hgs.asm; public class A { } package hgs.asm; //用于操作的类 public class AnoDesc { String name = "hgs"; int age = 100; @AutoWare A a; public void saySomething(String desc) { System.out.println("say:" + desc); } } //测试 package hgs.asm; import java.io.IOException; import java.lang.reflect.Field; import java.util.List; import org.objectweb.asm.ClassReader; import org.objectweb.asm.Type; import org.objectweb.asm.tree.AnnotationNode; import org.objectweb.asm.tree.ClassNode; import org.objectweb.asm.tree.FieldNode; public class Test { public static void test1() throws IOException, ClassNotFoundException, InstantiationException, IllegalAccessException, NoSuchFieldException, SecurityException { String clazz = "hgs.asm.AnoDesc"; Class> forName = Class.forName(clazz); AnoDesc newInstance = (AnoDesc)forName.newInstance(); //通过asm读取类 通过其属性api 来访问类的属性 方法 注解 ClassNode node = new ClassNode(); //node.superName ="org.objectweb.asm.ClassVisitor"; ClassReader reader = new ClassReader("hgs.asm.AnoDesc"); //ClassWriter writer = new ClassWriter(0); reader.accept(node,0); //node.accept(writer); //得到所有的属性 Listfields = node.fields; for(FieldNode fnd: fields) { String name = fnd.name; String desc = fnd.desc; Object value = fnd.value; Type tp = Type.getObjectType(desc); System.out.println("name:"+name); System.out.println("desc:"+desc); System.out.println("value:"+value); System.out.println("type:"+tp.getInternalName()); System.out.println(); //判断属性是否存在 AutoWare注解 List invisibleAnnotations = fnd.invisibleAnnotations; if(invisibleAnnotations!=null ) { for(AnnotationNode and : invisibleAnnotations) { System.out.println(" anotation:"+and.desc); System.out.println("equals:"+"Lhgs/asm/AutoWare;".equals(and.desc)); //存在的话 就把该属性初始化 if("Lhgs/asm/AutoWare;".equals(and.desc)) { String qiliName = tp.getInternalName().replaceFirst("L", "").replaceAll("/", "\\.").replace(";", ""); System.out.println("qulity name :"+ qiliName); Class> fi = Class.forName(qiliName); Field declaredField = forName.getDeclaredField(name); declaredField.set(newInstance,fi.newInstance() ); } } } } System.out.println(newInstance.a); } public static void main(String[] args) throws Exception{ test1(); } } 结果