VisitorLogProxy.java

/*
 * Copyright 1999-2015 dangdang.com.
 * <p>
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * </p>
 */

package com.dangdang.ddframe.rdb.sharding.parser.visitor;

import java.lang.reflect.Method;

import com.dangdang.ddframe.rdb.sharding.exception.ShardingJdbcException;
import com.dangdang.ddframe.rdb.sharding.parser.visitor.basic.mysql.AbstractMySQLVisitor;

import lombok.AccessLevel;
import lombok.NoArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

/**
 * SQL解析日志打印.
 * 
 * @author gaohongtao
 */
@NoArgsConstructor(access = AccessLevel.PRIVATE)
@Slf4j
public final class VisitorLogProxy {
    
    /**
     * 打印SQL解析调用树.
     * 
     * @param target 待增强类
     * @param <T> 泛型
     * @return 增强后的新类的对象
     */
    @SuppressWarnings("unchecked")
    public static <T> T enhance(final Class<T> target) {
        if (log.isTraceEnabled()) {
            Enhancer result = new Enhancer();
            result.setSuperclass(target);
            result.setCallback(new VisitorHandler());
            return (T) result.create();
        } else {
            try {
                return target.newInstance();
            } catch (final InstantiationException | IllegalAccessException ex) {
                log.error("create Visitor exception: {}", ex);
                throw new ShardingJdbcException(ex);
            }
        }
    }
    
    private static class VisitorHandler implements MethodInterceptor {
        
        private final StringBuilder hierarchyIndex = new StringBuilder();
        
        private Integer depth = 0;
        
        @Override
        public Object intercept(final Object enhancedObject, final Method method, final Object[] arguments, final MethodProxy methodProxy) throws Throwable {
            if (isPrintable(method)) {
                hierarchyIn();
                log.trace("{}visit node: {}", hierarchyIndex, arguments[0].getClass());
                log.trace("{}visit argument: {}", hierarchyIndex, arguments[0]);
            }
            Object result = methodProxy.invokeSuper(enhancedObject, arguments);
            if (isPrintable(method)) {
                AbstractMySQLVisitor visitor = (AbstractMySQLVisitor) enhancedObject;
                log.trace("{}endVisit node: {}", hierarchyIndex, arguments[0].getClass());
                log.trace("{}endVisit result: {}", hierarchyIndex, visitor.getParseContext().getParsedResult());
                log.trace("{}endVisit condition: {}", hierarchyIndex, visitor.getParseContext().getCurrentConditionContext());
                log.trace("{}endVisit SQL: {}", hierarchyIndex, visitor.getSQLBuilder());
                hierarchyOut();
            }
            return result;
        }
        
        private boolean isPrintable(final Method method) {
            return log.isTraceEnabled() && "visit".equals(method.getName());
        }
        
        private void hierarchyIn() {
            hierarchyIndex.append("  ").append(++depth).append(" ");
        }
        
        private void hierarchyOut() {
            hierarchyIndex.delete(hierarchyIndex.length() - 3 - depth.toString().length(), hierarchyIndex.length());
            depth--;
        }
    }
}