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();
}
}