Springboot使用SPI注册bean到spring容器的示例代码

2022-11-13 18:11:05 代码示例容器

MyDriver接口

public interface MyDriver {
    void getConnect();
}

MysqlDriver实现

public class MysqlDriver implements MyDriver{
    @Override
    public void getConnect() {
        System.out.println("connect");
    }
}

OracleDriver实现

public class OracleDriver implements MyDriver{
    @Override
    public void getConnect() {
        System.out.println("connect");
    }
}

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.support.*;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.util.StringUtils;
 
import java.io.BufferedReader;
import java.io.File;
import java.io.InputStreamReader;
import java.lang.reflect.Field;
import java.net.URL;
import java.NIO.charset.StandardCharsets;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
 
public class ExtensionLoader implements BeanDefinitionReGIStryPostProcessor, ApplicationContextAware {
 
    ApplicationContext context;
 
    BeanDefinitionRegistry beanDefinitionRegistry;
 
    ConcurrentHashMap<Class<?>, Map<String, Object>> EXTENSIONS = new ConcurrentHashMap<>();
 
    private static final String SPI_DIRECTORY = "META-INF/vtest/";
 
    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.context = applicationContext;
 
        ConfigurableApplicationContext configurableApplicationContext = (ConfigurableApplicationContext) context;
        beanDefinitionRegistry = (DefaultListableBeanFactory) configurableApplicationContext.getBeanFactory();
    }
 
    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry beanDefinitionRegistry) throws BeansException {
        try {
            ClassLoader classLoader = DefaultListableBeanFactory.class.getClassLoader();
            URL resource;
            File[] files;
 
            if (classLoader != null) {
                resource = classLoader.getResource(this.SPI_DIRECTORY);
            } else {
                resource = ClassLoader.getSystemResource(this.SPI_DIRECTORY);
            }
 
            files = new File(resource.getFile()).listFiles();
 
            for (int i = 0; i < files.length; i++) {
                Class<?> clazz = Class.forName(files[i].getName(), true, classLoader);
                EXTENSIONS.putIfAbsent(clazz, loadExtensionClass(clazz.getName()));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
 
    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
 
    }
 
    
    public Map<String, Object> getExtensions(Class type) {
        if (null == type) {
            throw new IllegalArgumentException("Extension Class is null");
        }
 
        if (!type.isInterface()) {
            throw new IllegalArgumentException("Extension Class is not an interface");
        }
 
        Map<String, Object> loader = EXTENSIONS.get(type);
        if (loader == null) {
            synchronized (ExtensionLoader.class) {
                loader = EXTENSIONS.get(type);
                if (loader == null) {
                    EXTENSIONS.putIfAbsent(type, loadExtensionClass(type.getName()));
                    loader = EXTENSIONS.get(type);
                }
            }
        }
        return loader;
    }
 
    
    private Map<String, Object> loadExtensionClass(String type) {
        Map<String, Object> extensionClasses = new HashMap<>();
        loadDirectory(extensionClasses, SPI_DIRECTORY, type);
        return extensionClasses;
    }
 
    
    private void loadDirectory(Map<String, Object> extensionClasses, String dir, String type) {
        String fileName = dir + type;
        try {
            Enumeration<URL> urls;
            ClassLoader classLoader = DefaultListableBeanFactory.class.getClassLoader();
            if (classLoader != null) {
                urls = classLoader.getResources(fileName);
            } else {
                urls = ClassLoader.getSystemResources(fileName);
            }
            if (urls != null) {
                while (urls.hasMoreElements()) {
                    URL resourcesURL = urls.nextElement();
                    loadResources(extensionClasses, classLoader, resourcesURL);
                }
            }
        } catch (Throwable t) {
        }
    }
 
    private void loadResources(Map<String, Object> extensionClasses, ClassLoader classLoader, URL resourceURL) {
        try {
            try (BufferedReader reader = new BufferedReader(new InputStreamReader(resourceURL.openStream(), StandardCharsets.UTF_8))) {
                String line;
                while ((line = reader.readLine()) != null) {
                    final int ci = line.indexOf('#');
                    if (ci >= 0) {
                        line = line.substring(0, ci);
                    }
                    line = line.trim();
                    if (line.length() > 0) {
                        try {
                            String name = null;
                            int i = line.indexOf('=');
                            if (i > 0) {
                                name = line.substring(0, i).trim();
                                line = line.substring(i + 1).trim();
                            }
                            if (line.length() > 0) {
                                loadClass(extensionClasses, resourceURL, Class.forName(line, true, classLoader), name);
                            }
                        } catch (Throwable t) {
                            IllegalStateException e = new IllegalStateException("Failed to load extension class (class line: " + line + ") in " + resourceURL + ", cause: " + t.getMessage(), t);
                        }
                    }
                }
            }
        } catch (Throwable t) {
        }
    }
 
    private void loadClass(Map<String, Object> extensionClasses, java.net.URL resourceURL, Class<?> clazz, String name) {
        if (StringUtils.isEmpty(name)) {
            throw new IllegalStateException("No such extension name for the class " + name + " in the config " + resourceURL);
        }
        Object o = extensionClasses.get(name);
        if (o == null) {
            Object bean = injectBeanToSpring(name, clazz);
            extensionClasses.put(name, bean);
        } else {
            throw new IllegalStateException("Duplicate extension name " + name + " on " + clazz.getName() + " and " + clazz.getName());
        }
    }
 
    
    private Object injectBeanToSpring(String name, Class<?> obj) {
        String beanName = name;
 
        BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(obj);
        GenericBeanDefinition definition = (GenericBeanDefinition) builder.getRawBeanDefinition();
        definition.setAutowireMode(GenericBeanDefinition.AUTOWIRE_BY_NAME);
        beanDefinitionRegistry.registerBeanDefinition(beanName, definition);
 
        // TODO: 2020/1/9  这里动态注入的bean并未将内部的@Autowired的bean依赖注入进去，如何解决？
 
        // 通过反射设置@Autowired标记的字段的值
 
        Object bean = context.getBean(beanName);
 
        Field[] declaredFields = obj.getDeclaredFields();
        for (Field field : declaredFields) {
            if (field.isAnnotationPresent(Autowired.class)) {
                Object aClass = context.getBean(field.getType());
 
                ReflectHelper.setFieldValue(bean, field.getName(), aClass);
            }
        }
 
        return bean;
    }
}

public class ReflectHelper {
 
    
    public static Object getFieldValue(Object obj, String fieldName) {
        Object result = null;
        Field field = ReflectHelper.getField(obj, fieldName);
        if (field != null) {
            field.setAccessible(true);
            try {
                result = field.get(obj);
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
        }
        return result;
    }
 
    
    private static Field getField(Object obj, String fieldName) {
        Field field = null;
        for (Class<?> clazz = obj.getClass(); clazz != Object.class; clazz = clazz.getSuperclass()) {
            try {
                field = clazz.getDeclaredField(fieldName);
                break;
            } catch (NoSuchFieldException e) {
                //这里不用做处理，子类没有该字段可能对应的父类有，都没有就返回null。
            }
        }
        return field;
    }
 
    
    public static void setFieldValue(Object obj, String fieldName,
                                     Object fieldValue) {
        Field field = ReflectHelper.getField(obj, fieldName);
        if (field != null) {
            try {
                field.setAccessible(true);
                field.set(obj, fieldValue);
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
        }
    }
}

Controller：

@RestController
@RequestMapping("/t")
@api(value = "测试服务", description = "")
public class TestController {
 
	// 切换不同的服务
    @Autowired
    @Qualifier("mysqlDriver")
    private MyDriver myDriver;
 
    @ApiOperation(value = "测试", notes = "基于Spring Boot实现的JAVA SPI机制的DEMO")
    @GetMapping("/spi")
    public String test() {
        myDriver.getConnect();
 
        return "ok";
    }
}

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Springboot使用SPI注册bean到spring容器的示例代码

目录

MyDriver接口

MysqlDriver实现

OracleDriver实现

Controller：