JavaBean在程序中的操作非常頻繁，但總有一些開源組件易于使用和擴展，為眾多開發人員提供了便利，下面一起來了解JSP 開發之Spring BeanUtils組件使用的知識。
JSP 開發之Spring BeanUtils組件使用
用于演示的javabean
import java.util.Date;public class People { private String name; private int age; private Date birth; public People(String name, int age, Date birth) { super(); this.name = name; this.age = age; this.birth = birth; } public People() { super(); // TODO Auto-generated constructor stub } @Override public String toString() { return "People [name=" + name + ", age=" + age + ", birth=" + birth + "]"; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public Date getBirth() { return birth; } public void setBirth(Date birth) { this.birth = birth; }}測試（所有測試只與源javabean屬性值有關，與目標javabean屬性值無關）
當源javabean屬性均有值時的目標javabean屬性復制情況
@Testpublic void springBeanUtilsTest(){ People oldPeople = new People("oldName",100,new Date()); People newPeople = new People(); //BeanUtils.copyProperties(Object source,Object target); BeanUtils.copyProperties(oldPeople, newPeople); System.out.println(oldPeople); System.out.println(newPeople);}輸出結果如下
People [name=oldName, age=100, birth=Wed Jul 19 18:46:13 CST 2017]People [name=oldName, age=100, birth=Wed Jul 19 18:46:13 CST 2017]
當源javabean非Date類型的屬性值為null時目標javabean屬性的復制情況
@Testpublic void springBeanUtilsTest(){ People oldPeople = new People(null,100,new Date()); People newPeople = new People("newName",20,null); //BeanUtils.copyProperties(Object source,Object target); BeanUtils.copyProperties(oldPeople, newPeople); System.out.println(oldPeople); System.out.println(newPeople);}輸出結果如下
注意:目標javabean中的非null屬性值被覆蓋為null了
People [name=null, age=100, birth=Wed Jul 19 19:04:48 CST 2017]People [name=null, age=100, birth=Wed Jul 19 19:04:48 CST 2017]
當源javabean中Date類型的屬性值為null時目標javabean中屬性值的復制情況
@Testpublic void springBeanUtilsTest(){ People oldPeople = new People("oldName",100,null); People newPeople = new People("newName",20,new Date()); //BeanUtils.copyProperties(Object source,Object target); BeanUtils.copyProperties(oldPeople, newPeople); System.out.println(oldPeople); System.out.println(newPeople);}輸出結果如下
People [name=oldName, age=100, birth=null]People [name=oldName, age=100, birth=null]
BeanUtils.copyProperties(Object source,Object target);方法有一個不足的地方，就是當source里的屬性對應的屬性值為null時，也會覆蓋掉target里相同屬性名的屬性，即使target中該屬性值已存在且不為null的屬性值，這顯然有些不合理，這是我們可以使用它的一個重載方法：
BeanUtils.copyProperties(Object source,Object target, String... ignoreProperties);
最后一個參數的含義是，復制屬性值時忽略的屬性名稱，所有我們只要找出source中屬性值為null的屬性名稱數組即可，方法如下：
/** * * @Title: getNullPropertyNames * @Description: 獲取一個對象中屬性值為null的屬性名字符串數組 * @param source * @return */public static String[] getNullPropertyNames (Object source) { final BeanWrapper src = new BeanWrapperImpl(source); java.beans.PropertyDescriptor[] pds = src.getPropertyDescriptors(); Set<String> emptyNames = new HashSet<String>(); for(java.beans.PropertyDescriptor pd : pds) { Object srcValue = src.getPropertyValue(pd.getName()); if (srcValue == null) emptyNames.add(pd.getName()); } String[] result = new String[emptyNames.size()]; return emptyNames.toArray(result);}測試
@Testpublic void copyBeanNotNull(){ People oldPeople = new People(null, 100, null); People newPeople = new People("newName", 20, new Date()); //BeanUtils.copyProperties(Object source,Object target, String... ignoreProperties); BeanUtils.copyProperties(oldPeople, newPeople, getNullPropertyNames(oldPeople)); System.out.println(oldPeople); System.out.println(newPeople); for(String key : getNullPropertyNames(oldPeople)){ System.out.println(key); }}輸出結果如下
People [name=null, age=100, birth=null]People [name=newName, age=100, birth=Wed Jul 19 23:31:05 CST 2017]namebirth我們看完了以上介紹的JSP 開發之Spring BeanUtils組件使用，可以關注錯新技術頻道小編之后推出的文章哦，希望大家要繼續加油。
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