Java反射通过Getter方法获取对象VO的属性值过程解析

这篇文章主要介绍了Java反射通过Getter方法获取对象VO的属性值过程解析,文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下

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）

FieldEntity

package com.nicchagil.util.fields;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;

public class FieldsCollector {

  public static Map<String, FieldEntity> getFileds(Object object)
      throws SecurityException, IllegalArgumentException, NoSuchMethodException,
      IllegalAccessException, InvocationTargetException {
    Class clazz = object.getClass();
    Field[] fields = clazz.getDeclaredFields();
    Map<String, FieldEntity> map = new HashMap<String, FieldEntity> ();

    for (int i = 0; i < fields.length; i++) {

      Object resultObject = invokeMethod(object, fields[i].getName(), null);
      map.put(fields[i].getName(), new FieldEntity(fields[i].getName(), resultObject, fields[i].getType()));
    }

    return map;
  }

  public static Object invokeMethod(Object owner, String fieldname,
      Object[] args) throws SecurityException, NoSuchMethodException,
      IllegalArgumentException, IllegalAccessException, InvocationTargetException {
    Class ownerClass = owner.getClass();

    Method method = null;
    method = ownerClass.getMethod(GetterUtil.toGetter(fieldname));

    Object object = null;
    object = method.invoke(owner);

    return object;
  }

}

主类，通过这个类的静态方法获取结果Map

FieldsCollector

package com.nicchagil.util.fields;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;

public class FieldsCollector {

  public static Map<String, FieldEntity> getFileds(Object object)
      throws SecurityException, IllegalArgumentException, NoSuchMethodException,
      IllegalAccessException, InvocationTargetException {
    Class clazz = object.getClass();
    Field[] fields = clazz.getDeclaredFields();
    Map<String, FieldEntity> map = new HashMap<String, FieldEntity> ();

    for (int i = 0; i < fields.length; i++) {

      Object resultObject = invokeMethod(object, fields[i].getName(), null);
      map.put(fields[i].getName(), new FieldEntity(fields[i].getName(), resultObject, fields[i].getType()));
    }

    return map;
  }

  public static Object invokeMethod(Object owner, String fieldname,
      Object[] args) throws SecurityException, NoSuchMethodException,
      IllegalArgumentException, IllegalAccessException, InvocationTargetException {
    Class ownerClass = owner.getClass();

    Method method = null;
    method = ownerClass.getMethod(GetterUtil.toGetter(fieldname));

    Object object = null;
    object = method.invoke(owner);

    return object;
  }

}

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

GetterUtil

package com.nicchagil.util.fields;

public class GetterUtil {

  /**
   * Get getter method name by field name
   * @param fieldname
   * @return
   */
  public static String toGetter(String fieldname) {

    if (fieldname == null || fieldname.length() == 0) {
      return null;
    }

    /* If the second char is upper, make 'get' + field name as getter name. For example, eBlog -> geteBlog */
    if (fieldname.length() > 2) {
      String second = fieldname.substring(1, 2);
      if (second.equals(second.toUpperCase())) {
        return new StringBuffer("get").append(fieldname).toString();
      }
    }

    /* Common situation */
    fieldname = new StringBuffer("get").append(fieldname.substring(0, 1).toUpperCase())
        .append(fieldname.substring(1)).toString();

    return fieldname;
  }

}

大功告成！！！

现在，写个VO作为模拟数据

User

import java.util.Date;

public class User {

  private String username;
  private String password;
  private String eBlog;
  private Date registrationDate;

  public String getUsername() {
    return username;
  }

  public void setUsername(String username) {
    this.username = username;
  }

  public String getPassword() {
    return password;
  }

  public void setPassword(String password) {
    this.password = password;
  }

  public String geteBlog() {
    return eBlog;
  }

  public void seteBlog(String eBlog) {
    this.eBlog = eBlog;
  }

  public Date getRegistrationDate() {
    return registrationDate;
  }

  public void setRegistrationDate(Date registrationDate) {
    this.registrationDate = registrationDate;
  }

}

最后，测试类，此类将直接调用FieldsCollector~~

Call

import java.util.Date;
import java.util.Map;

import com.nicchagil.util.fields.FieldEntity;
import com.nicchagil.util.fields.FieldsCollector;

public class Call {

  public static void main(String[] args) throws Exception {

    User user = new User();
    user.setUsername("user109");
    user.setPassword("pwd109");
    user.seteBlog("http://www.cnblogs.com/nick-huang/");
    user.setRegistrationDate(new Date());

    Map<String, FieldEntity> map = FieldsCollector.getFileds(user);
    System.out.println(map);

  }

}

Oh year， 成功了~~~

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