What is the difference between Service Provider Interface (SPI) and Application Programming Interface (API)? More specifically, for Java libraries, what makes them an API and/or SPI? the API is the description of classes/interfaces/methods/... that you call and use to achieve a goal the SPI is the description of classes/interfaces/methods/... that you extend and implement to achieve a goal Put differently, the API tells you what a specific class/method does for you and the SPI tells you what you must do to conform. Sometimes SPI and API overlap. For example in JDBC the Driver class is part of the SPI: If you simply want to use JDBC, you don't need to use it directly, but everyone who implements a JDBC driver must implement that class. The Connection interface on the other hand is both SPI and API: You use it routinely when you use a JDBC driver and it needs to be implemented by the developer of the JDBC driver。
JDK spi
使用jdk自带的ServiceLoader写一个示例：
一个接口
1 2 3 4
public interface Spi {
public void provide(); }
一个实现类
1 2 3 4 5 6 7
public class DefaultSpi implements Spi{
@Override public void provide() { System.out.println("默认spi实现"); } }
入口类
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
/** * 一个spi的demo * */ public class SpiDemoMain { public static void main( String[] args ) { ServiceLoader<Spi> spiServiceLoader = ServiceLoader.load(Spi.class);