利用jOOR簡化Java 反射使用

原文： http://lukaseder.wordpress.com/2011/12/29/a-neater-way-to-use-reflection-in-java/

Java的反射機制是Java一個非常強大的工具, 但是和大多數腳本語言相比, 使用起來卻是有種"懶婆娘的裹腳布——又臭又長"的感覺. 

比如在PHP語言中, 我們可能這樣寫:

// PHP
$method = 'my_method';
$field  = 'my_field';

// Dynamically call a method
$object->$method();
// Dynamically access a field
$object->$field;</pre> 
  
 
  
 在JavaScript語言中, 我們會這樣寫: 
  
 
  
// JavaScript
var method   = 'my_method';
var field    = 'my_field';

// Dynamically call a function
objectmethod;
// Dynamically access a field
object[field];</pre> 
  
 在Java中, 我們會這樣寫: 
  
 
  
 
  
String method = "my_method";
String field  = "my_field";

// Dynamically call a method
object.getClass().getMethod(method).invoke(object);
// Dynamically access a field
object.getClass().getField(field).get(object);</pre> 
  
 
  
 上面的代碼還沒有考慮到對各種異常的處理, 比如NullPointerExceptions, InvocationTargetExceptions, IllegalAccessExceptions, IllegalArgumentExceptions, SecurityExceptions. 以及對基本類型的處理. 但是大部分情況下, 這些都是不需要關心的. 
  
 
  
 為了解決這個問題, 于是有了這個工具: jOOR (Java Object Oriented Reflection). 
  
 
  
 對于這樣的Java代碼: 
  
 
  
// Classic example of reflection usage
try {
  Method m1 = department.getClass().getMethod("getEmployees");
  Employee employees = (Employee[]) m1.invoke(department);

for (Employee employee : employees) {
    Method m2 = employee.getClass().getMethod("getAddress");
    Address address = (Address) m2.invoke(employee);

Method m3 = address.getClass().getMethod("getStreet");
Street street = (Street) m3.invoke(address);

System.out.println(street);

}
}
// There are many checked exceptions that you are likely to ignore anyway
catch (Exception ignore) {
// ... or maybe just wrap in your preferred runtime exception:
  throw new RuntimeException(e);
}</pre> 
  
 
  
 使用 jOOR的寫法: 
  
 
  
 
  
Employee[] employees = on(department).call("getEmployees").get();

for (Employee employee : employees) {
  Street street = on(employee).call("getAddress").call("getStreet").get();
  System.out.println(street);
}</pre> 
  
 
  
 在Stack Overflow上相關的問題討論: 
  
 
  
 
  http://stackoverflow.com/questions/4385003/java-reflection-open-source/8672186 
  
 
  
 另一個例子: 
  
 
  
 
  
String world =
on("java.lang.String")  // Like Class.forName()
 .create("Hello World") // Call the most specific matching constructor
 .call("substring", 6)  // Call the most specific matching method
 .call("toString")      // Call toString()
 .get()                 // Get the wrapped object, in this case a String
 
  
 
  
 jOOR相關的信息, 請猛擊: 
  
 
  http://code.google.com/p/joor/ 
  
 
  
 轉自： 
  http://macrochen.iteye.com/blog/1347172