1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
|
/*
* Copyright (C) 2005 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.reflect;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.annotations.Beta;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Proxy;
/**
* Static utilities relating to Java reflection.
*
* @since 12.0
*/
@Beta
public final class Reflection {
/**
* Returns the package name of {@code clazz} according to the Java Language Specification (section
* 6.7). Unlike {@link Class#getPackage}, this method only parses the class name, without
* attempting to define the {@link Package} and hence load files.
*/
public static String getPackageName(Class<?> clazz) {
return getPackageName(clazz.getName());
}
/**
* Returns the package name of {@code classFullName} according to the Java Language Specification
* (section 6.7). Unlike {@link Class#getPackage}, this method only parses the class name, without
* attempting to define the {@link Package} and hence load files.
*/
public static String getPackageName(String classFullName) {
int lastDot = classFullName.lastIndexOf('.');
return (lastDot < 0) ? "" : classFullName.substring(0, lastDot);
}
/**
* Ensures that the given classes are initialized, as described in
* <a href="http://java.sun.com/docs/books/jls/third_edition/html/execution.html#12.4.2">
* JLS Section 12.4.2</a>.
*
* <p>WARNING: Normally it's a smell if a class needs to be explicitly initialized, because static
* state hurts system maintainability and testability. In cases when you have no choice while
* inter-operating with a legacy framework, this method helps to keep the code less ugly.
*
* @throws ExceptionInInitializerError if an exception is thrown during
* initialization of a class
*/
public static void initialize(Class<?>... classes) {
for (Class<?> clazz : classes) {
try {
Class.forName(clazz.getName(), true, clazz.getClassLoader());
} catch (ClassNotFoundException e) {
throw new AssertionError(e);
}
}
}
/**
* Returns a proxy instance that implements {@code interfaceType} by
* dispatching method invocations to {@code handler}. The class loader of
* {@code interfaceType} will be used to define the proxy class. To implement
* multiple interfaces or specify a class loader, use
* {@link Proxy#newProxyInstance}.
*
* @throws IllegalArgumentException if {@code interfaceType} does not specify
* the type of a Java interface
*/
public static <T> T newProxy(
Class<T> interfaceType, InvocationHandler handler) {
checkNotNull(handler);
checkArgument(interfaceType.isInterface(), "%s is not an interface", interfaceType);
Object object = Proxy.newProxyInstance(
interfaceType.getClassLoader(),
new Class<?>[] { interfaceType },
handler);
return interfaceType.cast(object);
}
private Reflection() {}
}
|
