mybatis通过拦截器动态的修改sql

比如你的orderInfo有个版本号，你需要每次修改的时候版本号增加1，如果手工添加比较麻烦，容易遗漏，可以通过拦截器实现。

这里适合通过mybatis根据实体类更新的情况，如果是手工写的update 代码，则可以把

parameter instanceof OrderInfo更换为

sql.contains(" order_info ")

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.beanutils.PropertyUtils;
import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.SqlCommandType;
import org.apache.ibatis.mapping.SqlSource;
import org.apache.ibatis.plugin.*;
import org.springframework.beans.factory.annotation.Autowired;

import java.util.Properties;

//只拦截update请求
@Intercepts({@Signature(
        type = Executor.class,
        method = "update",
        args = {MappedStatement.class, Object.class}
)})
@Slf4j
public class MybatisUpdateInterceptor implements Interceptor {

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        // 获取当前执行的SQL语句
        Object[] args = invocation.getArgs();
        MappedStatement mappedStatement = (MappedStatement) args[0];
        Object parameter = args[1];
        // 判断当前执行的SQL语句是否是修改orderInfo表的数据
        if (mappedStatement.getSqlCommandType().equals(SqlCommandType.UPDATE) && parameter instanceof OrderInfo) {
            //如果是修改order_info表，修改version
            PropertyUtils.setProperty(parameter, "version", null);
            BoundSql boundSql = mappedStatement.getBoundSql(parameter);
            String sql = boundSql.getSql();
            sql = sql.replace(" WHERE ", ",`version`=(version+1) WHERE ");
            BoundSql newBoundSql = new BoundSql(mappedStatement.getConfiguration(), sql, boundSql.getParameterMappings(), parameter);
            // 把新的查询放到statement里
            MappedStatement newMs = copyFromMappedStatement(mappedStatement, new BoundSqlSqlSource(newBoundSql));
            args[0] = newMs;
        }
        return invocation.proceed();
    }


    @Override
    public Object plugin(Object target) {
        return Plugin.wrap(target, this);
    }

    @Override
    public void setProperties(Properties properties) {
        // do nothing
    }

    private MappedStatement copyFromMappedStatement(MappedStatement ms, SqlSource newSqlSource) {
        MappedStatement.Builder builder = new MappedStatement.Builder(ms.getConfiguration(), ms.getId(), newSqlSource, ms.getSqlCommandType());
        builder.resource(ms.getResource());
        builder.fetchSize(ms.getFetchSize());
        builder.statementType(ms.getStatementType());
        builder.keyGenerator(ms.getKeyGenerator());
        if (ms.getKeyProperties() != null && ms.getKeyProperties().length > 0) {
            builder.keyProperty(ms.getKeyProperties()[0]);
        }
        builder.timeout(ms.getTimeout());
        builder.parameterMap(ms.getParameterMap());
        builder.resultMaps(ms.getResultMaps());
        builder.resultSetType(ms.getResultSetType());
        builder.cache(ms.getCache());
        builder.flushCacheRequired(ms.isFlushCacheRequired());
        builder.useCache(ms.isUseCache());
        return builder.build();
    }

    private static class BoundSqlSqlSource implements SqlSource {
        private BoundSql boundSql;

        public BoundSqlSqlSource(BoundSql boundSql) {
            this.boundSql = boundSql;
        }

        @Override
        public BoundSql getBoundSql(Object parameterObject) {
            return boundSql;
        }
    }
}

添加MybatisConfig，注入拦截器

/**
 * mybatis配置
 */
@Configuration
public class MybatisConfig {
    /**
     * 注册拦截器
     */
    @Bean
    public MybatisUpdateInterceptor mybatisInterceptor() {
        MybatisUpdateInterceptor interceptor = new MybatisUpdateInterceptor();
        return interceptor;
    }
}