自定義註解+策略模式，實現不一樣表的寫操做！

案例：

一、利用阿里的開源數據庫同步工具-canal來解析不一樣的數據庫表binlog日誌，解析完成的數據，咱們要入庫不一樣的數據庫，不一樣的表。
二、每一個表對應一個Mapper類，插入不一樣的表，咱們須要選擇不一樣的Mapper來執行同一個函數：insertSelective
三、普通的完成方式，咱們須要根據不一樣的表名採用「if」條件判斷，選擇不一樣的Mapper，這樣的代碼是比較冗餘的。

如何利用自定義註解來實現？

一、定義一個接口：IProcessor

package com.jane.binlog.dao;

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

    int updateSelective(T record);
}

二、定義一個註解：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、每一個Mapper增長註解：@ProcessorMapper

一、註解的值就是表的名字。
二、Mapper實現接口IProcessor，傳入操做對象的類型

import java.util.Date;

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

四、調用文件

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<>();

    //定義表和對象的關係
    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，注入帶有自定義註解的全部mapper到一個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));
            }
        }
    }

    /**
     * 數據寫入操做
     * @param table
     * @param data
     * @param op
     */
    public void binlogInsert(String table, Map<String, Object> data, String op) {
        try {
                    //獲取表對應的對象類
            Class clazz = map.get(table);
                        //組裝對象數據
            Object obj = this.assumePosSale(data, clazz);
                        //實現寫操做
            IProcessor processor = mapperMap.get(table);
            processor.insertSelective(obj);
        } catch(Exception e) {
            throw e;
        }
    }

    /**
     * 把數據map轉化爲對應表對象
     * @param data
     * @param clazz
     * @return
     */
    private Object assumePosSale(Map<String, Object> data, Class clazz) {
        return JSONObject.parseObject(JSONObject.toJSONString(data), clazz);
    }

}