1. Study of the Class object, Filed object (corresponding to data), Method of the image (corresponding to the function), Constructor object (corresponding to the constructor).
2.Declared be used to obtain private data and methods, but is printed using setAccessible ( to true) ; to check to ignore access modifier.
3.FS5 () function has a point to note is the same address, the reason I wrote in a comment in the.
#FS practice profile # 1. The full name of the class you need to create objects and methods need to be performed is defined in the configuration file # 2 is loaded in the program reads the configuration file # 3. Use reflective technology to load class files into the memory # 4. create Object # 5. execution method # #
className=bean.Admin
methodName=eat
Filed learning objects
/ **
* Learning java reflection mechanism
* Field, learning objects
* /
@Test
public void FS1 () throws a NoSuchFieldException, IllegalAccessException {
Class userClass = User.class;
Field, [] = userClass.getFields Fields (); // get all public member object
for (Field, Field: Fields)
{
System.out.println (Field);
}
Field, field1 = userClass.getField ( "FS"); // in accordance with the variable name acquisition
/ *
Field, operation
1. set
sET
2. Get
GET
* /
the User new new user1 = the User ();
System.out.println (field1.get (user1));
field1.set (user1, "Dada");
System.out.println (field1.get (user1));
// ignore modifiers can get to the private
Field, [] = Full userClass.getDeclaredFields ();
for (Field, Field, : Full)
{
System.out.println (Field,);
}
// get a single one ignores modifier
Field, privateField = userClass.getDeclaredField ( "the above mentioned id");
// print but private, need to ignore to check access modifier
privateField.setAccessible (true); // reflective violent
System.out.println (privateField.get (user1));
}
Constructor object of study
/ **
* constructor reflection acquisition
* /
@Test
public void FS2 () throws a NoSuchMethodException, IllegalAccessException, a InvocationTargetException, an InstantiationException is {
Class userClass = User.class;
// get all
Constructor [] constructors = userClass.getConstructors () ;
for (the constructor constructor: Constructors)
{
System.out.println (constructor);
}
// get a single
the constructor constructor = userClass.getConstructor (Integer.class, String.class);
System.out.println (constructor);
// use get the constructor to create objects
Object user = constructor.newInstance (5, " dada");
System.out.println (user.toString ());
/ *
empty argument constructor
* /
the Constructor constructor1 userClass.getConstructor = ();
System.out.println (constructor);
Object constructor1.newInstance user1 = ();
System.out.println (user1.toString ());
System.out.println ( "upper empathy");
// with the same token, Class this method is to facilitate an empty argument constructor method call
Object user2 = userClass .newInstance ();
System.out.println (user2.toString ());
// violent reflection constructor.setAccessible ();
}
Method of learning objects
/ **
* Get reflection method
* Method,
* /
@Test
public void FS3 () throws a NoSuchMethodException, a InvocationTargetException, IllegalAccessException {
Class userClass = User.class;
// Get Class Name
String className = userClass.getName ();
the System.out .println (className);
// Get all public methods
method, [] = userClass.getMethods methods ();
for (method, method: methods)
{
// is also printed in the Obj method
System.out.println (method);
/ / Get method name
System.out.println (method.getName ());
}
// Get method method name return value
Method eat = userClass.getMethod("eat");
Method eat1= userClass.getMethod("eat",int.class);
User user=new User();
eat.invoke(user);//执行方法
eat1.invoke(user,1);//执行方法
}
And reflection profiles using
/ **
* reflection profiles and using
* /
@Test
public void FS4 () throws IOException, a ClassNotFoundException, IllegalAccessException, an InstantiationException is, a NoSuchMethodException, a InvocationTargetException {
// load configuration file. 1.
The Properties Pro new new = the Properties ();
// Get profile classes directory ClassLoader class
ClassLoader TestUserFS.class.getClassLoader classLoader = ();
// get the input stream
the InputStream resourceAsStream = ClassLoader.getResourceAsStream ( "FS.properties");
// loading
pro.load (resourceAsStream);
// 2. Get the data defined in the configuration file
System.out.println (methodName);
String className = pro.getProperty ( "className" );
Pro.getProperty methodName = String ( "methodName");
.. 3 // loaded into memory class
Class = userClass the Class.forName (className);
.. 4 // Create Object
Object obj = userClass.newInstance ();
.. 5 // Get an object method
method, method = userClass.getMethod (methodName);
// Get function with parameters that eat
method, the method1 = userClass.getMethod (methodName, int.class);
//. 6 to perform the method.
Method.invoke (obj);
the method1. Invoke (obj,. 1);
}
Three common ways: Class.forName () function, I used before when using JDBC, the other two species rarely.
/ **
* Notes
* 1.Class.forName ( "full class name")
* 2. Object .getClass (): Get Method
* 3. Class Name .class: property class obtained by class name
* /
@Test
public void FS5 () throws a ClassNotFoundException, IllegalAccessException, an InstantiationException is, a NoSuchMethodException, a InvocationTargetException {
// profile. 1 for
Class = objClass1 the Class.forName ( "bean.User");
System.out.println (objClass1);
Object user1 = objClass1. the newInstance ();
Method, the method1 = objClass1.getMethod ( "EAT");
method1.invoke (user1);
. // 2-byte codes used for obtaining an existing object
Class objClass2 = User.class;
System.out.println ( objClass2);
// 3 for parameter passing
the User = new new USER3 the User ();
Class objClass3 = user3.getClass ();
System.out.println (objClass3);
/ *
* three is the same address
* Why?
* Because the class after loading into memory only once, so you get him when only a
* /
System.out.println (objClass1.hashCode ());
System.out.println (objClass2.hashCode ());
System.out .println (objClass3.hashCode ());
}
Summary: java reflection mechanism and configuration files is really handy, as I learned before log4 configuration error in the console output helped me a lot.
The java Junit let me write the code more convenient.