自定义注解+策略模式，实现不一样表的写操做！

案例：

一、利用阿里的开源数据库同步工具-canal来解析不一样的数据库表binlog日志，解析完成的数据，咱们要入库不一样的数据库，不一样的表。
二、每一个表对应一个Mapper类，插入不一样的表，咱们须要选择不一样的Mapper来执行同一个函数：insertSelective
三、普通的完成方式，咱们须要根据不一样的表名采用“if”条件判断，选择不一样的Mapper，这样的代码是比较冗余的。

如何利用自定义注解来实现？

一、定义一个接口：IProcessor

package com.jane.binlog.dao;

public interface IProcessor<T> {
    int insertSelective(T record);

    int updateSelective(T record);
}

二、定义一个注解：ProcessorMapper

package com.jane.binlog.dao;

import java.lang.annotation.*;

@Target({ ElementType.METHOD, ElementType.TYPE })
@Retention(RetentionPolicy.RUNTIME)
@Inherited
public @interface ProcessorMapper {

    String value() default "";
}

三、每一个Mapper增长注解：@ProcessorMapper

一、注解的值就是表的名字。
二、Mapper实现接口IProcessor，传入操做对象的类型

import java.util.Date;

@Repository
@ProcessorMapper("pos_sale")
public interface PosSaleMapper extends IProcessor<PosSale> {
   int insert(PosSale record);
}

四、调用文件

package com.jane.binlog.service;

import com.alibaba.fastjson.JSONObject;
import com.jane.binlog.dao.IProcessor;
import com.jane.binlog.dao.ProcessorMapper;
import com.jane.binlog.entity.PosSale;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Service;

import javax.annotation.PostConstruct;
import java.util.HashMap;
import java.util.Map;

@Service
public class PosSaleService {

    private static Logger LOG = LoggerFactory.getLogger(PosSaleService.class);

    public static Map<String, Class> map = new HashMap<>();

    //定义表和对象的关系
    static {
        map.put("pos_sale", PosSale.class);
    }

    private Map<String, IProcessor> mapperMap = new HashMap<String, IProcessor>();

    @Autowired
    private ApplicationContext applicationContext;

    //利用spring上下文，注入带有自定义注解的全部mapper到一个hashmap中。
    @PostConstruct
    public void init() {
        String[] classNames = applicationContext.getBeanNamesForAnnotation(ProcessorMapper.class);
        for (String name: classNames) {
            Class<?> type = applicationContext.getType(name);
            boolean posSaleMapper = type.isAnnotationPresent(ProcessorMapper.class);
            if (posSaleMapper) {
                String value = type.getAnnotation(ProcessorMapper.class).value();
                mapperMap.put(value, (IProcessor) applicationContext.getBean(name));
            }
        }
    }

    /**
     * 数据写入操做
     * @param table
     * @param data
     * @param op
     */
    public void binlogInsert(String table, Map<String, Object> data, String op) {
        try {
                    //获取表对应的对象类
            Class clazz = map.get(table);
                        //组装对象数据
            Object obj = this.assumePosSale(data, clazz);
                        //实现写操做
            IProcessor processor = mapperMap.get(table);
            processor.insertSelective(obj);
        } catch(Exception e) {
            throw e;
        }
    }

    /**
     * 把数据map转化为对应表对象
     * @param data
     * @param clazz
     * @return
     */
    private Object assumePosSale(Map<String, Object> data, Class clazz) {
        return JSONObject.parseObject(JSONObject.toJSONString(data), clazz);
    }

}