在Java中方法引用作为方法参数线程安全吗? [英] Are method References as method parameters thread safe in Java
问题描述
我有以下情况:
interface ValueBinding<T> {
public void setValue(T input);
}
public enum FacesBinding {
VALUE;
public void bindString(ValueBinding<String> fcn, HttpServletRequest req, String param){
try {
String val = req.getParameter(param);
if( val != null )
fcn.setValue(val);
} catch (Exception e) { }
}
public void bindBoolean(ValueBinding<Boolean> fcn, HttpServletRequest req, String param){
try {
fcn.setValue(req.getParameter(param) != null);
} catch (Exception e) { }
}
public void bindInt(ValueBinding<Integer> fcn, HttpServletRequest req, String param){
try {
int val = Integer.parseInt(req.getParameter(param));
fcn.setValue(val);
} catch (Exception e) { }
}
public void bindLong(ValueBinding<Long> fcn, HttpServletRequest req, String param){
try {
long val = Long.parseLong(req.getParameter(param));
fcn.setValue(val);
} catch (Exception e) { }
}
...
...
}
我在这样的多线程"环境中使用它:
并发线程正在调用此方法
@Override // concurrent Threads are calling this method
public Category initData(FacesContext facesContext) throws Exception {
Category entity = new Category();
HttpServletRequest req = facesContext.getRequest();
FacesBinding.VALUE.bindLong(entity::setId, req, Table.Category.Field.ID.name());
FacesBinding.VALUE.bindString(entity::setName, req, Table.Category.Field.NAME.name());
FacesBinding.VALUE.bindInt(entity::setPosition, req, Table.Category.Field.POSITION.name());
FacesBinding.VALUE.bindBoolean(entity::setLocalized, req, Table.Category.Field.LOCALIZED.name());
return entity;
}
是
FacesBinding.VALUE.bindLong(entity::setId, req, Table.Category.Field.ID.name());
entity::setId作为枚举对象(单例)中方法的参数时，100％线程安全 )?
注意:
entity::setId
entity::setName
entity::setPosition
...等所有这些方法都是标准的Java setter方法
public void setId(long id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}
....
更新:
具体来说: ARECategory entity = new Category();
entity.setId(5);//thread safe for sure
100％等于
FacesBinding.VALUE.bindLong(entity::setId, ...);
具有FacesBinding ist Singleton和bindLong(entity::setId, ...)中的Reference方法是否使其成为线程不安全的事实吗?
如果您的setId方法是线程安全的，则方法引用调用将是线程安全的，仅此而已.
方法参考是创建ValueBinding对象的简便方法.当它们被编译时，将有一个私有的内部类来实现您的功能接口并调用您指定的方法.由于您指定了属于对象的方法，因此该内部类也将等效于，具有接受您的Category对象的构造函数和一个私有字段来存储它(我说等效于因为默认情况下，如果可以证明并选择其他任何实现，则实现不限于此行为.
i have the following scenario:
interface ValueBinding<T> {
public void setValue(T input);
}
public enum FacesBinding {
VALUE;
public void bindString(ValueBinding<String> fcn, HttpServletRequest req, String param){
try {
String val = req.getParameter(param);
if( val != null )
fcn.setValue(val);
} catch (Exception e) { }
}
public void bindBoolean(ValueBinding<Boolean> fcn, HttpServletRequest req, String param){
try {
fcn.setValue(req.getParameter(param) != null);
} catch (Exception e) { }
}
public void bindInt(ValueBinding<Integer> fcn, HttpServletRequest req, String param){
try {
int val = Integer.parseInt(req.getParameter(param));
fcn.setValue(val);
} catch (Exception e) { }
}
public void bindLong(ValueBinding<Long> fcn, HttpServletRequest req, String param){
try {
long val = Long.parseLong(req.getParameter(param));
fcn.setValue(val);
} catch (Exception e) { }
}
...
...
}
and i use it in a "multithreaded" Environment like this:
concurrent Threads are calling this method
@Override // concurrent Threads are calling this method
public Category initData(FacesContext facesContext) throws Exception {
Category entity = new Category();
HttpServletRequest req = facesContext.getRequest();
FacesBinding.VALUE.bindLong(entity::setId, req, Table.Category.Field.ID.name());
FacesBinding.VALUE.bindString(entity::setName, req, Table.Category.Field.NAME.name());
FacesBinding.VALUE.bindInt(entity::setPosition, req, Table.Category.Field.POSITION.name());
FacesBinding.VALUE.bindBoolean(entity::setLocalized, req, Table.Category.Field.LOCALIZED.name());
return entity;
}
is
FacesBinding.VALUE.bindLong(entity::setId, req, Table.Category.Field.ID.name());
100% Thread safe when i pass a method reference(interface) entity::setId as parameter of a method in enum Object (Singleton)?
NOTE:
entity::setId
entity::setName
entity::setPosition
...etc. ALL these methods are standard java setter methods
public void setId(long id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}
....
UPDATE:
to be concrete: ARE
Category entity = new Category();
entity.setId(5);//thread safe for sure
100% equal to
FacesBinding.VALUE.bindLong(entity::setId, ...);
does the fact that FacesBinding ist Singleton and the method Reference in bindLong(entity::setId, ...) makes it thread-unsafe??
Your method reference call will be thread-safe if your setId method is thread-safe, nothing more and nothing less.
Method reference is a fancy shorthand for creating your ValueBinding objects. When they are compiled, there will be a private inner class of sorts that implements your functional interface and calls the method you specified. Since you specified method that belongs to an object, this inner class will also be equivalent to having constructor that accepts your Category object, and a private field to store it (I said equivalent to because by default implementations are not limited to this behavior if they can justify and choose any other).
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