SPI，Service Provider Interface，服务提供者接口。

Animal 接口

---

 package com.rockcode.www.spi;

 public interface Animal {

 void speek();

}

Dog 类

---

 package com.rockcode.www.spi;

 public class Dog implements Animal {

 public void speek() {

System.out.println("....Dog....");

}

 }

SPI规范

---

 

com.rockcode.www.spi.Animal 文件内容 com.rockcode.www.spi.Dog

注意，文件必须位于 Jar 包的 META-INF/services 下面，名称与接口名相同

ServiceLoader

---

 

ServiceLoader<Animal> loader = ServiceLoader.load(Animal.class);

for (Animal an : loader) {

an.speek();

}

 

源码

---

 

URL url = ClassLoader.getSystemClassLoader().getResource(

"META-INF/services/" + Animal.class.getName());

InputStream ins = null;

BufferedReader br = null;

try {

ins = url.openStream();

br = new BufferedReader(new InputStreamReader(ins));

 

String ln = br.readLine();

System.out.println(ln);

 

try {

Class<?> c = Class.forName(ln);

try {

Object o = c.newInstance();

Dog d = (Dog) c.cast(o);

d.speek();

} catch (InstantiationException e) {

e.printStackTrace();

} catch (IllegalAccessException e) {

e.printStackTrace();

}

} catch (ClassNotFoundException e) {

e.printStackTrace();

}

 

} catch (IOException e) {

e.printStackTrace();

} finally {

if (br != null)

try {

br.close();

} catch (IOException e) {

e.printStackTrace();

}

if (ins != null)

try {

ins.close();

} catch (IOException e) {

e.printStackTrace();

}

}