问题描述
在我的Java项目中，我想以编程方式找出使用给定API中的哪些类。有没有一个好方法呢？通过源代码解析或字节码解析可能吗？因为反射没有任何用处，我担心。
In a Java Project of mine, I would like to find out programmatically which classes from a given API are used. Is there a good way to do that? Through source code parsing or bytecode parsing maybe? Because Reflection won't be of any use, I'm afraid.
为了简单起见：没有通配符导入（ import com。 mycompany.api。*; ）我的项目中的任何地方，没有完全限定的字段或变量定义（ private com.mycompany.api.MyThingy thingy; ）也没有任何构造。鉴于这些限制，我认为它可以归结为解析import语句。有没有一种首选方法可以做到这一点？
To make things simpler: there are no wildcard imports (import com.mycompany.api.*;) anywhere in my project, no fully qualified field or variable definitions (private com.mycompany.api.MyThingy thingy;) nor any Class.forName(...) constructs. Given these limitations, it boils down to parsing import statements, I guess. Is there a preferred approach to do this?
推荐答案
您可以使用的 class（信不信由你）。该类实际上是用于替换字节码中出现的所有类名。然而，出于您的目的，它不需要替换任何东西。
You can discover the classes using ASM's Remapper class (believe it or not). This class is actually meant to replace all occurrences of a class name within bytecode. For your purposes, however, it doesn't need to replace anything.
这可能没有多大意义，所以这里有一个例子......
This probably doesn't make a whole lot of sense, so here is an example...
首先，您创建一个 Remapper 的子类，其唯一的目的是拦截对 mapType（String） 方法，记录其参数供以后使用。
First, you create a subclass of Remapper whose only purpose in life is to intercept all calls to the mapType(String) method, recording its argument for later use.
public class ClassNameRecordingRemapper extends Remapper {
private final Set<? super String> classNames;
public ClassNameRecordingRemapper(Set<? super String> classNames) {
this.classNames = classNames;
}
@Override
public String mapType(String type) {
classNames.add(type);
return type;
}
}
现在你可以编写类似的方法这个：
Now you can write a method like this:
public Set<String> findClassNames(byte[] bytecode) {
Set<String> classNames = new HashSet<String>();
ClassReader classReader = new ClassReader(bytecode);
ClassWriter classWriter = new ClassWriter(classReader, 0);
ClassNameRecordingRemapper remapper = new ClassNameRecordingRemapper(classNames);
classReader.accept(remapper, 0);
return classNames;
}
实际获取所有类的字节码是你的责任。
It's your responsibility to actually obtain all classes' bytecode.
我接受这个答案，但是上面的代码不太正确，我将插入我使用的方式：
I am accepting this answer, but as the above code is not quite correct, I will insert the way I used this:
public static class Collector extends Remapper{
private final Set<Class<?>> classNames;
private final String prefix;
public Collector(final Set<Class<?>> classNames, final String prefix){
this.classNames = classNames;
this.prefix = prefix;
}
/**
* {@inheritDoc}
*/
@Override
public String mapDesc(final String desc){
if(desc.startsWith("L")){
this.addType(desc.substring(1, desc.length() - 1));
}
return super.mapDesc(desc);
}
/**
* {@inheritDoc}
*/
@Override
public String[] mapTypes(final String[] types){
for(final String type : types){
this.addType(type);
}
return super.mapTypes(types);
}
private void addType(final String type){
final String className = type.replace('/', '.');
if(className.startsWith(this.prefix)){
try{
this.classNames.add(Class.forName(className));
} catch(final ClassNotFoundException e){
throw new IllegalStateException(e);
}
}
}
@Override
public String mapType(final String type){
this.addType(type);
return type;
}
}
public static Set<Class<?>> getClassesUsedBy(
final String name, // class name
final String prefix // common prefix for all classes
// that will be retrieved
) throws IOException{
final ClassReader reader = new ClassReader(name);
final Set<Class<?>> classes =
new TreeSet<Class<?>>(new Comparator<Class<?>>(){
@Override
public int compare(final Class<?> o1, final Class<?> o2){
return o1.getName().compareTo(o2.getName());
}
});
final Remapper remapper = new Collector(classes, prefix);
final ClassVisitor inner = new EmptyVisitor();
final RemappingClassAdapter visitor =
new RemappingClassAdapter(inner, remapper);
reader.accept(visitor, 0);
return classes;
}
这是一个使用以下方法测试它的主要类：
Here's a main class to test it using:
public static void main(final String[] args) throws Exception{
final Collection<Class<?>> classes =
getClassesUsedBy(Collections.class.getName(), "java.util");
System.out.println("Used classes:");
for(final Class<?> cls : classes){
System.out.println(" - " + cls.getName());
}
}
这是输出：
Used classes:
- java.util.ArrayList
- java.util.Arrays
- java.util.Collection
- java.util.Collections
- java.util.Collections$1
- java.util.Collections$AsLIFOQueue
- java.util.Collections$CheckedCollection
- java.util.Collections$CheckedList
- java.util.Collections$CheckedMap
- java.util.Collections$CheckedRandomAccessList
- java.util.Collections$CheckedSet
- java.util.Collections$CheckedSortedMap
- java.util.Collections$CheckedSortedSet
- java.util.Collections$CopiesList
- java.util.Collections$EmptyList
- java.util.Collections$EmptyMap
- java.util.Collections$EmptySet
- java.util.Collections$ReverseComparator
- java.util.Collections$ReverseComparator2
- java.util.Collections$SelfComparable
- java.util.Collections$SetFromMap
- java.util.Collections$SingletonList
- java.util.Collections$SingletonMap
- java.util.Collections$SingletonSet
- java.util.Collections$SynchronizedCollection
- java.util.Collections$SynchronizedList
- java.util.Collections$SynchronizedMap
- java.util.Collections$SynchronizedRandomAccessList
- java.util.Collections$SynchronizedSet
- java.util.Collections$SynchronizedSortedMap
- java.util.Collections$SynchronizedSortedSet
- java.util.Collections$UnmodifiableCollection
- java.util.Collections$UnmodifiableList
- java.util.Collections$UnmodifiableMap
- java.util.Collections$UnmodifiableRandomAccessList
- java.util.Collections$UnmodifiableSet
- java.util.Collections$UnmodifiableSortedMap
- java.util.Collections$UnmodifiableSortedSet
- java.util.Comparator
- java.util.Deque
- java.util.Enumeration
- java.util.Iterator
- java.util.List
- java.util.ListIterator
- java.util.Map
- java.util.Queue
- java.util.Random
- java.util.RandomAccess
- java.util.Set
- java.util.SortedMap
- java.util.SortedSet
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