package org.apache.ibatis.plugin;
import java.util.Properties;
public interface Interceptor {
//intercept方法就是要進(jìn)行攔截的時(shí)候要執(zhí)行的方法。
  Object intercept(Invocation invocation) throws Throwable;
//plugin方法是攔截器用于封裝目標(biāo)對(duì)象的，通過該方法我們可以返回目標(biāo)對(duì)象本身，也可以返回一個(gè)它的代理。當(dāng)返回的是代理的時(shí)候我們可以對(duì)其中的方法進(jìn)行攔截來調(diào)用intercept方法，當(dāng)然也可以調(diào)用其他方法。
  Object plugin(Object target);
//setProperties方法是用于在Mybatis配置文件中指定一些屬性的。
  void setProperties(Properties properties);

}  

package com.shinemo.insurance.common.config;
 
import org.apache.ibatis.plugin.Interceptor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
 
@Configuration
public class TableShardConfig {

    /**
     * 注冊(cè)插件
     */
    @Bean
    public Interceptor tableShardInterceptor() {
        return new TableShardInterceptor();
    }

}

package com.shinemo.insurance.common.annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(value = { ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
public @interface TableShard {

    // 表前綴名
    String tableNamePrefix();

    // 值
    String value() default "";

    // 是否是字段名，如果是需要解析請(qǐng)求參數(shù)改字段名的值（默認(rèn)否）
    boolean fieldFlag() default false;

}

@Mapper
@TableShard(tableNamePrefix = "t_insurance_video_people_", value = "deviceId", fieldFlag = true)
public interface InsuranceVideoPeopleMapper {
 
//VideoPeople對(duì)象中包含deviceId字段
  int insert(VideoPeople videoPeople);
}

package com.shinemo.insurance.common.config;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.util.Map;

import com.shinemo.insurance.common.annotation.TableShard;
import com.shinemo.insurance.common.util.HashUtil;

import org.apache.ibatis.binding.MapperMethod;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.mapping.BoundSql;
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.reflection.DefaultReflectorFactory;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.ReflectorFactory;
import org.apache.ibatis.reflection.SystemMetaObject;
@Intercepts({ @Signature(type = StatementHandler.class, method = "prepare", args = { Connection.class,
                                                                                    Integer.class }) })
public class TableShardInterceptor implements Interceptor {
    private static final ReflectorFactory DEFAULT_REFLECTOR_FACTORY = new DefaultReflectorFactory();
    @Override
    public Object intercept(Invocation invocation) throws Throwable {

        // MetaObject是mybatis里面提供的一個(gè)工具類，類似反射的效果
        MetaObject metaObject = getMetaObject(invocation);
        BoundSql boundSql = (BoundSql) metaObject.getValue("delegate.boundSql");
        MappedStatement mappedStatement = (MappedStatement) metaObject
            .getValue("delegate.mappedStatement");

        // 獲取Mapper執(zhí)行方法
        Method method = invocation.getMethod();

        // 獲取分表注解
        TableShard tableShard = getTableShard(method, mappedStatement);

        // 如果method與class都沒有TableShard注解或執(zhí)行方法不存在，執(zhí)行下一個(gè)插件邏輯
        if (tableShard == null) {
            return invocation.proceed();
        }

        //獲取值，此值就是拿的注解上value值，注解上value設(shè)定的值，并在傳入對(duì)象中獲取，根據(jù)業(yè)務(wù)可以選擇適當(dāng)?shù)闹导纯?，我選取此值的目的是同一臺(tái)設(shè)備的值存入一張表中，有hash沖突的值也存在一張表中
        String value = tableShard.value();
        //value是否字段名，如果是，需要解析請(qǐng)求參數(shù)字段名的值
        boolean fieldFlag = tableShard.fieldFlag();

        if (fieldFlag) {
            //獲取請(qǐng)求參數(shù)
            Object parameterObject = boundSql.getParameterObject();

            if (parameterObject instanceof MapperMethod.ParamMap) {
                // ParamMap類型邏輯處理
                MapperMethod.ParamMap parameterMap = (MapperMethod.ParamMap) parameterObject;
                // 根據(jù)字段名獲取參數(shù)值
                Object valueObject = parameterMap.get(value);
                if (valueObject == null) {
                    throw new RuntimeException(String.format("入?yún)⒆侄?s無匹配", value));
                }
                //替換sql
                replaceSql(tableShard, valueObject, metaObject, boundSql);

            } else {
                // 單參數(shù)邏輯

                //如果是基礎(chǔ)類型拋出異常
                if (isBaseType(parameterObject)) {
                    throw new RuntimeException("單參數(shù)非法，請(qǐng)使用@Param注解");
                }

                if (parameterObject instanceof Map) {
                    Map<String, Object> parameterMap = (Map<String, Object>) parameterObject;
                    Object valueObject = parameterMap.get(value);
                    //替換sql
                    replaceSql(tableShard, valueObject, metaObject, boundSql);
                } else {
                    //非基礎(chǔ)類型對(duì)象
                    Class<?> parameterObjectClass = parameterObject.getClass();
                    Field declaredField = parameterObjectClass.getDeclaredField(value);
                    declaredField.setAccessible(true);
                    Object valueObject = declaredField.get(parameterObject);
                    //替換sql
                    replaceSql(tableShard, valueObject, metaObject, boundSql);
                }
            }

        } else {//無需處理parameterField
            //替換sql
            replaceSql(tableShard, value, metaObject, boundSql);
        }
        //把原有的簡(jiǎn)單查詢語(yǔ)句替換為分表查詢語(yǔ)句了，現(xiàn)在是時(shí)候?qū)⒊绦虻目刂茩?quán)交還給Mybatis下一個(gè)攔截器處理
        return invocation.proceed();
    }

    /**
     * @description:
     * @param target
     * @return: Object
     */
    @Override
    public Object plugin(Object target) {
        // 當(dāng)目標(biāo)類是StatementHandler類型時(shí)，才包裝目標(biāo)類，否者直接返回目標(biāo)本身, 減少目標(biāo)被代理的次數(shù)
        if (target instanceof StatementHandler) {
            return Plugin.wrap(target, this);
        } else {
            return target;
        }
    }

    /**
     * @description: 基本數(shù)據(jù)類型驗(yàn)證，true是，false否
     * @param object
     * @return: boolean
     */
    private boolean isBaseType(Object object) {
        if (object.getClass().isPrimitive() || object instanceof String || object instanceof Integer
            || object instanceof Double || object instanceof Float || object instanceof Long
            || object instanceof Boolean || object instanceof Byte || object instanceof Short) {
            return true;
        } else {
            return false;
        }
    }
    /**
     * @description: 替換sql
     * @param tableShard 分表注解
     * @param value      值
     * @param metaObject mybatis反射對(duì)象
     * @param boundSql   sql信息對(duì)象
     * @return: void
     */
    private void replaceSql(TableShard tableShard, Object value, MetaObject metaObject,
                            BoundSql boundSql) {
        String tableNamePrefix = tableShard.tableNamePrefix();
        //        // 獲取策略class
        //        Class<? extends ITableShardStrategy> strategyClazz = tableShard.shardStrategy();
        //        // 從spring ioc容器獲取策略類
        //        ITableShardStrategy tableShardStrategy = SpringBeanUtil.getBean(strategyClazz);
        // 生成分表名
        String shardTableName = generateTableName(tableNamePrefix, (String) value);
        // 獲取sql
        String sql = boundSql.getSql();
        // 完成表名替換
        metaObject.setValue("delegate.boundSql.sql",
            sql.replaceAll(tableNamePrefix, shardTableName));
    }

    /**
     * 生成表名
     *
     * @param tableNamePrefix 表名前綴
     * @param value           價(jià)值
     * @return {@link String}
     */
    private String generateTableName(String tableNamePrefix, String value) {

//我們分了1024張表
        int prime = 1024;
//hash取模運(yùn)算過后，鎖定目標(biāo)表
        int rotatingHash = HashUtil.rotatingHash(value, prime);
        return tableNamePrefix + rotatingHash;
    }
    /**
     * @description: 獲取MetaObject對(duì)象-mybatis里面提供的一個(gè)工具類，類似反射的效果
     * @param invocation
     * @return: MetaObject
     */
    private MetaObject getMetaObject(Invocation invocation) {
        StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
        // MetaObject是mybatis里面提供的一個(gè)工具類，類似反射的效果
        MetaObject metaObject = MetaObject.forObject(statementHandler,
            SystemMetaObject.DEFAULT_OBJECT_FACTORY,
            SystemMetaObject.DEFAULT_OBJECT_WRAPPER_FACTORY, DEFAULT_REFLECTOR_FACTORY);

        return metaObject;
    }
    /**
     * @description: 獲取分表注解
     * @param method
     * @param mappedStatement
     * @return: TableShard
     */
    private TableShard getTableShard(Method method,
                                     MappedStatement mappedStatement) throws ClassNotFoundException {
        String id = mappedStatement.getId();
        // 獲取Class
        final String className = id.substring(0, id.lastIndexOf("."));
        // 分表注解
        TableShard tableShard = null;
        // 獲取Mapper執(zhí)行方法的TableShard注解
        tableShard = method.getAnnotation(TableShard.class);
        // 如果方法沒有設(shè)置注解，從Mapper接口上面獲取TableShard注解
        if (tableShard == null) {
            // 獲取TableShard注解
            tableShard = Class.forName(className).getAnnotation(TableShard.class);
        }
        return tableShard;
    }
}