t*********e
发帖数: 630 | 1 Wikipedia 谈到 dependency injenction 的缺点：
1. Dependency injection can make code difficult to trace (read) because it
separates behavior from construction. This means developers must refer to
more files to follow how a system performs.[citation needed]
2. Dependency injection typically requires more lines of code to accomplish
the same behavior legacy code would.[citation needed]
3. Dependency injection diminishes encapsulation by requiring users of a
system to know how it works and not merely what it does.[5]
4. Dependency injection increases coupling by requiring the user of a
subsystem to provide for the needs of that subsystem.[6]
1 & 2 没有问题。3 & 4 是什么情况？怎么感觉 DI 不要求客户了解 dependency 的细
节?
On the contrary, it increases encapsulation and decreases coupling? |
t*********e
发帖数: 630 | 2 后面接着讲到 injection 的三种方式，constructor injection, setter injection
and interface injection. For instance,
Class Client {
private Service service;
public void setService(Service service) {
this.service = service;
}
}
Or
Class Client {
private Service service;
public Client(Service service) {
this.service = service
}
}
在 JEE 里面， 好像一行就解决了. 不用什么 constructor 或 setter method.
Class Client {
@Inject
private Service service;
}
怎么跟 wiki 上面说的不一样？
accomplish
【在 t*********e 的大作中提到】
: Wikipedia 谈到 dependency injenction 的缺点：
: 1. Dependency injection can make code difficult to trace (read) because it
: separates behavior from construction. This means developers must refer to
: more files to follow how a system performs.[citation needed]
: 2. Dependency injection typically requires more lines of code to accomplish
: the same behavior legacy code would.[citation needed]
: 3. Dependency injection diminishes encapsulation by requiring users of a
: system to know how it works and not merely what it does.[5]
: 4. Dependency injection increases coupling by requiring the user of a
: subsystem to provide for the needs of that subsystem.[6]
|
z****e
发帖数: 54598 | 3 第一种和第二种都是不用reflection
并用xml配置的
第三种是直接annotation，实现用了reflection
reflection可以直接访问私有变量
然后塞入reference
以前没有annotation的时候，第三种需要写到xml里面去
这中间有一个历史发展的过程，所以不同时期都不太一样
不过越来越简单倒是没错，所以你用最后一种就好了 |
t*********e
发帖数: 630 | 4 谢谢。
DI 减少了很多 new 的使用，挺好的。
【在 z****e 的大作中提到】
: 第一种和第二种都是不用reflection
: 并用xml配置的
: 第三种是直接annotation，实现用了reflection
: reflection可以直接访问私有变量
: 然后塞入reference
: 以前没有annotation的时候，第三种需要写到xml里面去
: 这中间有一个历史发展的过程，所以不同时期都不太一样
: 不过越来越简单倒是没错，所以你用最后一种就好了
|
