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 name
10 private String fieldname;
11
12 // field value
13 private Object value;
14
15 // field value‘s class type
16 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 = 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 = 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 @Override
70 public String toString() {
71 return "FieldEntity [fieldname=" + fieldname + ", value=" + value
72 + ", clazz=" + clazz + ", errorMsg=" + errorMsg + "]";
73 }
74
75 }
FieldEntity
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 }
FieldsCollector
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 }
GetterUtil
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 }
User
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 }
Call
Oh year， 成功了~~~
Java反射获取对象VO的属性值（通过Getter方法）
时间： 2024-11-11 04:29:22