マイバティスインターセプター

package org.apache.ibatis.plugin;
import java.util.Properties; 
public interface Interceptor { 
    Object intercept(Invocation invocation) throws Throwable; 
    Object plugin(Object target);
    void setProperties(Properties properties);
}

package org.apache.ibatis.plugin;
 
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import org.apache.ibatis.reflection.ExceptionUtil;
 
public class Plugin implements InvocationHandler {
 
    private Object target;
    private Interceptor interceptor;
    private Map<Class<?>, Set<Method>> signatureMap;
 
    private Plugin(Object target, Interceptor interceptor, Map<Class<?>, Set<Method>> signatureMap) {
        this.target = target;
        this.interceptor = interceptor;
        this.signatureMap = signatureMap;
    }
 
    public static Object wrap(Object target, Interceptor interceptor) {
        //解析获取需要拦截的类以及方法{*}
        Map<Class<?>, Set<Method>> signatureMap = getSignatureMap(interceptor);
        Class<?> type = target.getClass();
        //解析type是否存在需要拦截的接口{*}
        Class<?>[] interfaces = getAllInterfaces(type, signatureMap);
        //决定返回的对象是否为代理{*}
        if (interfaces.length > 0) {
            return Proxy.newProxyInstance(
                type.getClassLoader(),
                interfaces,
                new Plugin(target, interceptor, signatureMap));
        }
        //返回原目标对象
        return target;
    }
 
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        try {
            Set<Method> methods = signatureMap.get(method.getDeclaringClass());
            //如果当前执行的方法是定义的需要拦截的方法，则把目标对象，要拦截的方法以及参数封装为一个Invocation对象传递给拦截器方法intercept;
            //Invocation中定义了定义了一个proceed方法，其逻辑就是调用当前方法，所以如果在intercept中需要继续调用当前方法的话可以调用invocation的procced方法;
            if (methods != null && methods.contains(method)) {
                return interceptor.intercept(new Invocation(target, method, args));
            }
            return method.invoke(target, args);
        } catch (Exception e) {
            throw ExceptionUtil.unwrapThrowable(e);
        }
    }
 
    //根据注解解析需要拦截的方法
    //两个重要的注解：@Intercepts以及其值其值@Signature（一个数组）
    //@Intercepts用于表明当前的对象是一个Interceptor
    //@Signature则表明要拦截的接口、方法以及对应的参数类型。
    private static Map<Class<?>, Set<Method>> getSignatureMap(Interceptor interceptor) {
        Intercepts interceptsAnnotation = interceptor.getClass().getAnnotation(Intercepts.class);
        if (interceptsAnnotation == null) { // issue #251
            throw new PluginException("No @Intercepts annotation was found in interceptor " + interceptor.getClass().getName());
        }
        Signature[] sigs = interceptsAnnotation.value();
        Map<Class<?>, Set<Method>> signatureMap = new HashMap<Class<?>, Set<Method>>();
        for (Signature sig : sigs) {
            Set<Method> methods = signatureMap.get(sig.type());
            if (methods == null) {
                methods = new HashSet<Method>();
                signatureMap.put(sig.type(), methods);
            }
            try {
                Method method = sig.type().getMethod(sig.method(), sig.args());
                methods.add(method);
            } catch (NoSuchMethodException e) {
                throw new PluginException("Could not find method on " + sig.type() + " named " + sig.method() + ". Cause: " + e, e);
            }
        }
        return signatureMap;
    }
 
    private static Class<?>[] getAllInterfaces(Class<?> type, Map<Class<?>, Set<Method>>  signatureMap) {
        Set<Class<?>> interfaces = new HashSet<Class<?>>();
        while (type != null) {
            for (Class<?> c : type.getInterfaces()) {
                if (signatureMap.containsKey(c)) {
                    interfaces.add(c);
                }
            }
            type = type.getSuperclass();
        }
        return interfaces.toArray(new Class<?>[interfaces.size()]);
    }
}

package com.mybatis.interceptor;
 
import java.sql.Connection;
import java.util.Properties;
 
import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.plugin.Intercepts;
import org.apache.ibatis.plugin.Invocation;
import org.apache.ibatis.plugin.Plugin;
import org.apache.ibatis.plugin.Signature;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
 
@Intercepts( {
@Signature(method = "query", type = Executor.class, args = {
MappedStatement.class, Object.class, RowBounds.class,
ResultHandler.class })}) 
public class TestInterceptor implements Interceptor {
    public Object intercept(Invocation invocation) throws Throwable {
        Object result = invocation.proceed();
        return result;
    }
 
    public Object plugin(Object target) {
        return Plugin.wrap(target, this);
    }
 
    public void setProperties(Properties properties) {
        String p = properties.getProperty("property");
    }
}

<plugins>
    <plugin interceptor="com.mybatis.interceptor.TestInterceptor">
        <property name="property" value="拦截器配置"/>
    </plugin>
</plugins>