java通过反射+javassist获得方法所有信息(返回值、方法名、参数类型列表、参数列表)

亦凉 2021-06-24 14:34 373阅读 0赞

众所周知，使用java的反射无法获得方法参数名列表，只能获得方法参数类型列表，在网上研究了一下，发现有下面两种方式实现：

方案一：使用反射+javassit库

static void javassistGetInfo() throws Exception{
    		 Class<?> clazz = Class.forName("fanshe.Person");
    		 ClassPool pool = ClassPool.getDefault();  
    		 CtClass cc = pool.get(clazz.getName());  
    		 
    		 Method[] declaredMethods = clazz.getDeclaredMethods();
    		 for (Method mt:declaredMethods) {
    			 String modifier = Modifier.toString(mt.getModifiers());
    			 Class<?> returnType = mt.getReturnType();
    			 String name = mt.getName();
    			 Class<?>[] parameterTypes = mt.getParameterTypes();
    			 
    			 System.out.print("\n"+modifier+" "+returnType.getName()+" "+name+" (");
    			 
    			 
    			 //CtMethod[] declaredMethods1 = cc.getDeclaredMethods();
    			 CtMethod ctm = cc.getDeclaredMethod(name);
    			 MethodInfo methodInfo = ctm.getMethodInfo();
    			 CodeAttribute codeAttribute = methodInfo.getCodeAttribute();
    			 LocalVariableAttribute attribute = (LocalVariableAttribute)codeAttribute.getAttribute(LocalVariableAttribute.tag);
    			 int pos = Modifier.isStatic(ctm.getModifiers()) ? 0 : 1;
    			 for (int i=0;i<ctm.getParameterTypes().length;i++) {
    				 System.out.print(parameterTypes[i]+" "+attribute.variableName(i+pos));
    				 if (i<ctm.getParameterTypes().length-1) {
    					 System.out.print(",");
    				 }
    			 }
    			 
    			 System.out.print(")");
    			 
    			 Class<?>[] exceptionTypes = mt.getExceptionTypes();
    			 if (exceptionTypes.length>0) {
    					System.out.print(" throws ");
    					int j=0;
    					for (Class<?> cl:exceptionTypes) {
    						System.out.print(cl.getName());
    						if (j<exceptionTypes.length-1) {
    							System.out.print(",");
    						}
    						j++;
    					}
    				}
    		 }
    		 
    	}

方案二：使用spring的LocalVariableTableParameterNameDiscoverer，相比于javassit，这种方式要简单太多，所以推荐使用这种

import java.lang.reflect.Method;  
    import org.springframework.core.LocalVariableTableParameterNameDiscoverer;  
      
    public class GetParamNames {  
        public static void main(String[] args) {  
            LocalVariableTableParameterNameDiscoverer u =   
                new LocalVariableTableParameterNameDiscoverer();  
            Demo demo = new Demo();  
            Method[] methods = demo.getClass().getDeclaredMethods();  
            String[] params = u.getParameterNames(methods[0]);  
            for (int i = 0; i < params.length; i++) {  
                System.out.println(params[i]);  
            }  
        }  
    }