- 大家是不是经常遇到一种情况，比如两个对象，Member和MemberView，很多时候我们都有可能进行相互转换，那么我们常用的方法就是，把其中一个中的值挨个get出来，然后再挨个set到另一个中去，接下来我介绍的这种方法就可以解决这种问题造成的困扰，多的不说，看下面代码：
package copyPojoDemo;public class Member{ private String username; private String password; private String truename; private String nickname; private String gender; private int age; @Override public String toString(){ return (username==null?"":"username:" + username) + (password==null?"":" password:" + password) + (truename==null?"":" truename:" + truename) + (nickname==null?"":" nickname:" + nickname) + (gender==null?"":" gender:" + gender) + " age:" + age; }} package copyPojoDemo;public class MemberView{ private String username; private String password; private String truename; private String nickname; private String gender; private int age;} package copyPojoDemo;import java.lang.reflect.Field;import java.util.ArrayList;import java.util.List;public class ReflectionDemo{ public static void main(String args[]){ MemberView fromObject = new MemberView(); fromObject.setUsername("sunchenbin"); fromObject.setPassword("111111"); fromObject.setAge(21); fromObject.setGender("男"); fromObject.setNickname("墨白"); String[] fields = new String[]{}; // 没有设置属性，默认去对比两个对象 //String[] fields = new String[]{"username","password","gender"}; try{ // 将一个对象转换成另一个对象，并把指定的属性值传递给这个对象，如果不指定默认去匹配两个对象的属性，存在则赋值 Member member = (Member) constructObject(fromObject,new Member(),fields); System.out.println(member.toString()); }catch (Exception e){ // TODO Auto-generated catch block e.printStackTrace(); } } private static Object constructObject(Object fromObject,Object toObject,String[] fields) throws Exception{ // 数据源的class Class fromClass = fromObject.getClass(); // 目标的class Class toClass = toObject.getClass(); for (String field : fields){ try{ // 获取fromClass的Field Field fromDeclaredField = fromClass.getDeclaredField(field); fromDeclaredField.setAccessible(true); // 从fromClass中获取属性的值 Object value = fromDeclaredField.get(fromObject); // 获取toClass的Field Field toDeclaredField = toClass.getDeclaredField(field); toDeclaredField.setAccessible(true); // 将fromClass中该属性的值设置给toClass中的该属性 toDeclaredField.set(toObject, value); }catch (NoSuchFieldException e){ System.out.println(field+"属性不存在"); e.printStackTrace(); } } // 如果没有传递属性过来，那么默认对比from和to中的属性，存在的进行赋值操作 if(fields.length == 0){ Field[] fromDeclaredFields = fromClass.getDeclaredFields(); Field[] toDeclaredFields = toClass.getDeclaredFields(); List fromList = new ArrayList (); List toList = new ArrayList (); // 取出from中所有field for (Field field : fromDeclaredFields){ field.setAccessible(true); fromList.add(field.getName()); } // 取出to中所有field for (Field field : toDeclaredFields){ field.setAccessible(true); toList.add(field.getName()); } // 循环from属性list for (String name : fromList){ // to中是否包含该属性 if(toList.contains(name)){ // 包含先进行取值 Field fromDeclaredField = fromClass.getDeclaredField(name); fromDeclaredField.setAccessible(true); Object value = fromDeclaredField.get(fromObject); // 进行赋值操作 Field toDeclaredField = toClass.getDeclaredField(name); toDeclaredField.setAccessible(true); toDeclaredField.set(toObject, value); } } } return toObject; }} 以上基本就可以实现我们想要达到的效果了。
- 还有一种场合，程序执行时，要动态加载某个类并执行方法，那么看下面代码：
package initLoadDemo;public class TestClass{ public double eachOrtherToAdd(Integer one,Double two,Integer three){ return one+two+three; }} package initLoadDemo;import java.lang.reflect.Method;public class ReflectionDemo{ public static void main(String args[]){ String className = "initLoadDemo.TestClass"; String methodName = "eachOrtherToAdd"; String[] paramTypes = new String[]{ "Integer","Double","int"}; String[] paramValues = new String[]{ "1","4.3321","5"}; // 动态加载对象并执行方法 initLoadClass(className, methodName, paramTypes, paramValues); } @SuppressWarnings("rawtypes") private static void initLoadClass(String className,String methodName,String[] paramTypes,String[] paramValues){ try{ // 根据calssName得到class对象 Class cls = Class.forName(className); // 实例化对象 Object obj = cls.newInstance(); // 根据参数类型数组得到参数类型的Class数组 Class[] parameterTypes = constructTypes(paramTypes); // 得到方法 Method method = cls.getMethod(methodName, parameterTypes); // 根据参数类型数组和参数值数组得到参数值的obj数组 Object[] parameterValues = constructValues(paramTypes,paramValues); // 执行这个方法并返回obj值 Object returnValue = method.invoke(obj, parameterValues); System.out.println("结果："+returnValue); }catch (Exception e){ // TODO Auto-generated catch block e.printStackTrace(); } } private static Object[] constructValues(String[] paramTypes,String[] paramValues){ Object[] obj = new Object[paramTypes.length]; for (int i = 0; i < paramTypes.length; i++){ if(paramTypes[i] != null && !paramTypes[i].trim().equals("")){ if ("Integer".equals(paramTypes[i]) || "int".equals(paramTypes[i])){ obj[i] = Integer.parseInt(paramValues[i]); }else if ("Double".equals(paramTypes[i]) || "double".equals(paramTypes[i])){ obj[i] = Double.parseDouble(paramValues[i]); }else if ("Float".equals(paramTypes[i]) || "float".equals(paramTypes[i])){ obj[i] = Float.parseFloat(paramValues[i]); }else{ obj[i] = paramTypes[i]; } } } return obj; } @SuppressWarnings("rawtypes") private static Class[] constructTypes(String[] paramTypes){ Class[] cls = new Class[paramTypes.length]; for (int i = 0; i < paramTypes.length; i++){ if(paramTypes[i] != null && !paramTypes[i].trim().equals("")){ if ("Integer".equals(paramTypes[i]) || "int".equals(paramTypes[i])){ cls[i] = Integer.class; }else if ("Double".equals(paramTypes[i]) || "double".equals(paramTypes[i])){ cls[i] = Double.class; }else if ("Float".equals(paramTypes[i]) || "float".equals(paramTypes[i])){ cls[i] = Float.class; }else{ cls[i] = String.class; } } } return cls; }} 详解就不说了，说起java的反射机制，基本就会想到4个类，Field、Constractor、Method、Class，依次是分别封装了反射的属性、构造函数、方法，剩下的Class就不多说了，基本掌握这的应用就OK了，至于业务场景还有很多。