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Java反射获取对象VO的属性值(通过Getter方法)
有时候,需要动态获取对象的属性值。
比如,给你一个List,要你遍历这个List的对象的属性,而这个List里的对象并不固定。比如,这次User,下次可能是Company。
e.g. 这次我需要做一个Excel导出的工具类,导出的批量数据是以List类型传入的,List里的对象自然每次都不同,这取决于需要导出什么信息。
为了使用方便,将对象的属性名与属性值存于Map当中,使用时就可以直接遍历Map了。
此次的思路是通过反射和Getter方法取得值,然后记录在一个Map当中。
Kick start...
将对象的属性名与属性值存于Map当中,以key,value的形式存在,而value并不希望以单一类型(如String)存在(因为涉及多种类型),所以用一个FieldEntity的自定义类(此类包含属性名,属性值,属性值类型 等属性)
1 package com.nicchagil.util.fields; 2 3 4 import java.util.ArrayList; 5 import java.util.List; 6 7 public class FieldEntity { 8 9 // field name10 private String fieldname;11 12 // field value13 private Object value;14 15 // field value‘s class type16 private Class clazz;17 18 private List<String> errorMsg = new ArrayList<String> ();19 20 public String getFieldname() {21 return fieldname;22 }23 24 public void setFieldname(String fieldname) {25 this.fieldname = fieldname;26 }27 28 public Object getValue() {29 return value;30 }31 32 public void setValue(Object value) {33 this.value =http://www.mamicode.com/ value;34 }35 36 public Class getClazz() {37 return clazz;38 }39 40 public void setClazz(Class clazz) {41 this.clazz = clazz;42 }43 44 public List<String> getErrorMsg() {45 return errorMsg;46 }47 48 public void setErrorMsg(List<String> errorMsg) {49 this.errorMsg = errorMsg;50 }51 52 public FieldEntity() {53 super();54 }55 56 public FieldEntity(String fieldname, Object value, Class clazz) {57 super();58 this.fieldname = fieldname;59 this.value =http://www.mamicode.com/ value;60 this.clazz = clazz;61 }62 63 private FieldEntity(String fieldname, List<String> errorMsg) {64 super();65 this.fieldname = fieldname;66 this.errorMsg = errorMsg;67 }68 69 @Override70 public String toString() {71 return "FieldEntity [fieldname=" + fieldname + ", value="http://www.mamicode.com/+ value72 + ", clazz=" + clazz + ", errorMsg=" + errorMsg + "]";73 }74 75 }
主类,通过这个类的静态方法获取结果Map
1 package com.nicchagil.util.fields; 2 3 4 import java.lang.reflect.Field; 5 import java.lang.reflect.InvocationTargetException; 6 import java.lang.reflect.Method; 7 import java.util.HashMap; 8 import java.util.Map; 9 10 public class FieldsCollector {11 12 public static Map<String, FieldEntity> getFileds(Object object) 13 throws SecurityException, IllegalArgumentException, NoSuchMethodException, 14 IllegalAccessException, InvocationTargetException {15 Class clazz = object.getClass();16 Field[] fields = clazz.getDeclaredFields();17 Map<String, FieldEntity> map = new HashMap<String, FieldEntity> ();18 19 for (int i = 0; i < fields.length; i++) {20 21 Object resultObject = invokeMethod(object, fields[i].getName(), null);22 map.put(fields[i].getName(), new FieldEntity(fields[i].getName(), resultObject, fields[i].getType()));23 }24 25 return map;26 }27 28 public static Object invokeMethod(Object owner, String fieldname,29 Object[] args) throws SecurityException, NoSuchMethodException, 30 IllegalArgumentException, IllegalAccessException, InvocationTargetException {31 Class ownerClass = owner.getClass();32 33 Method method = null;34 method = ownerClass.getMethod(GetterUtil.toGetter(fieldname));35 36 Object object = null;37 object = method.invoke(owner);38 39 return object;40 }41 42 }
为了代码清楚些,将一些工具方法独立一下,如field name到getter name的转换方法
1 package com.nicchagil.util.fields; 2 3 public class GetterUtil { 4 5 /** 6 * Get getter method name by field name 7 * @param fieldname 8 * @return 9 */10 public static String toGetter(String fieldname) {11 12 if (fieldname == null || fieldname.length() == 0) {13 return null;14 }15 16 /* If the second char is upper, make ‘get‘ + field name as getter name. For example, eBlog -> geteBlog */17 if (fieldname.length() > 2) {18 String second = fieldname.substring(1, 2);19 if (second.equals(second.toUpperCase())) {20 return new StringBuffer("get").append(fieldname).toString();21 }22 }23 24 /* Common situation */25 fieldname = new StringBuffer("get").append(fieldname.substring(0, 1).toUpperCase())26 .append(fieldname.substring(1)).toString();27 28 return fieldname;29 }30 31 }
大功告成!!!
现在,写个VO作为模拟数据
1 import java.util.Date; 2 3 public class User { 4 5 private String username; 6 private String password; 7 private String eBlog; 8 private Date registrationDate; 9 10 public String getUsername() {11 return username;12 }13 14 public void setUsername(String username) {15 this.username = username;16 }17 18 public String getPassword() {19 return password;20 }21 22 public void setPassword(String password) {23 this.password = password;24 }25 26 public String geteBlog() {27 return eBlog;28 }29 30 public void seteBlog(String eBlog) {31 this.eBlog = eBlog;32 }33 34 public Date getRegistrationDate() {35 return registrationDate;36 }37 38 public void setRegistrationDate(Date registrationDate) {39 this.registrationDate = registrationDate;40 }41 42 }
最后,测试类,此类将直接调用FieldsCollector~~
1 import java.util.Date; 2 import java.util.Map; 3 4 import com.nicchagil.util.fields.FieldEntity; 5 import com.nicchagil.util.fields.FieldsCollector; 6 7 8 9 public class Call {10 11 public static void main(String[] args) throws Exception {12 13 User user = new User();14 user.setUsername("user109");15 user.setPassword("pwd109");16 user.seteBlog("http://www.cnblogs.com/nick-huang/");17 user.setRegistrationDate(new Date());18 19 Map<String, FieldEntity> map = FieldsCollector.getFileds(user);20 System.out.println(map);21 22 }23 24 }
Oh year, 成功了~~~
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