Mybatis支持GRPC protobuf

一时失言乱红尘 2022-05-19 09:38 276阅读 0赞

最近公司项目rpc使用Google grpc 作为rpc框架，数据传输DTO对象统一使用proto来定义，但由于DTO层的model和DAO层的model 在很大程度上是可以复用的，所以在DAO 层也想使用proto来定义，项目中ORM框架使用到了Mybatis框架，想要在Mybatis上支持grpc proto 需要处理那些工作呢？

Mapper Api 定义：

** int** save(Promotion promotion);//注意这里定义的是具体Model类，但在Mapper.xml中parameterType则是Model$Builder类，目的用来获取插入数据时将数据库生成的自增ID返回，只所以是keyProperty 等于“id\_” 是因为protobuf 生成的model属性进行了修改属性名称。

查询数据

Promotion getById(**int** id);

由于原生Mybatis 本身不支持proto api的方式，所以为了让Mybatis可以灵活的支持proto,所以我们需要开发proto plugin来实现。

在mybatis-config.xml配置中增加插件配置

<?xml version="1.0" encoding="UTF-8"?>
    <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
    <configuration>
    	<settings>
    		
    		<setting name="mapUnderscoreToCamelCase" value="true" />
    	</settings>
    	<typeHandlers />
    	<plugins>
            
    		<plugin interceptor="mybatis.plugins.ProtobufInterceptor" />
    	</plugins>
    </configuration>

import java.sql.Statement;
    import java.util.List;
    import java.util.Properties;
    import org.apache.ibatis.executor.resultset.DefaultResultSetHandler;
    import org.apache.ibatis.executor.resultset.ResultSetHandler;
    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 com.google.common.collect.Lists;
    import com.google.protobuf.GeneratedMessageV3;
    
    // Mybatis支持对Executor、StatementHandler、PameterHandler和ResultSetHandler 接口进行拦截
    @Intercepts({@Signature(type = ResultSetHandler.class, method = "handleResultSets",
        args = {Statement.class}),})
    public class ProtobufInterceptor implements Interceptor {
    
      public Object intercept(Invocation invocation) throws Throwable {
        DefaultResultSetHandler value = (DefaultResultSetHandler) invocation.getTarget();
        Object result = invocation.getMethod().invoke(value, invocation.getArgs());
        if (result != null) {
          if (List.class.isAssignableFrom(result.getClass())) {
            List<?> list = (List<?>) result;
            return this.process(list);
          }
        }
        return result;
      }
    
      private List<?> process(List<?> list) {
        if (list.size() > 0) {
          if (GeneratedMessageV3.Builder.class.isAssignableFrom(list.get(0).getClass())) {
            List<Object> resultList = Lists.newArrayList();
            for (Object val : list) {
              @SuppressWarnings("rawtypes")
              Object rtnVal = ((GeneratedMessageV3.Builder) val).build();
              resultList.add(rtnVal);
            }
            return resultList;
          }
        }
        return list;
      }
    
      @Override
      public Object plugin(Object target) {
        return Plugin.wrap(target, this);
      }
    
      @Override
      public void setProperties(Properties properties) {}
    
    }

有时候我们数据库的数据类型和proto中定义的数据类型不一致的，我们需要转换处理，例如：枚举类型

当数据插入数据到DB时，需要将Enum类型转换成数字类型存储到DB中，在查询时又需要将数字转到到枚举类型

这时候就需要自定义Mybatis提供的BaseTypeHandler 来实现自定义类型解析处理了。

例如： 自定义枚举类型

package hander;
    
    import java.lang.reflect.Method;
    import java.sql.CallableStatement;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import org.apache.ibatis.type.BaseTypeHandler;
    import org.apache.ibatis.type.JdbcType;
    import org.apache.ibatis.type.MappedJdbcTypes;
    import org.apache.ibatis.type.MappedTypes;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import com.google.protobuf.ProtocolMessageEnum;
    
    /**
     * 通用枚举转换处理
     * 
     * @author KEVIN LUAN
     *
     */
    @MappedJdbcTypes(value = {JdbcType.TINYINT})
    @MappedTypes({ProtocolMessageEnum.class})
    public class EnumHander extends BaseTypeHandler<ProtocolMessageEnum> {
      public Class<?> type;
      private Method method;
      private static final Logger LOGGER = LoggerFactory.getLogger(EnumHander.class);
    
      public EnumHander(Class<?> type) throws NoSuchMethodException, SecurityException {
        this.type = type;
        try {
          this.method = type.getMethod("forNumber", int.class);
        } catch (Exception e) {
          LOGGER.error("type:`" + type + "` getMethod:`forNumber` ERROR", e);
        }
      }
    
      public EnumHander() {}
    
      @Override
      public void setNonNullParameter(PreparedStatement ps, int i, ProtocolMessageEnum parameter,
          JdbcType jdbcType) throws SQLException {
        ps.setInt(i, parameter.getNumber());
      }
    
      private ProtocolMessageEnum forNumber(int value) {
        try {
          return (ProtocolMessageEnum) method.invoke(null, value);
        } catch (Exception e) {
          LOGGER.error("type:`" + type + "`.forNumber() ERROR", e);
          throw new RuntimeException("type:`" + type + "`.forNumber() ERROR", e);
        }
      }
    
      @Override
      public ProtocolMessageEnum getNullableResult(ResultSet rs, String columnName)
          throws SQLException {
        int value = rs.getInt(columnName);
        return forNumber(value);
      }
    
      @Override
      public ProtocolMessageEnum getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
        int value = rs.getInt(columnIndex);
        return forNumber(value);
      }
    
      @Override
      public ProtocolMessageEnum getNullableResult(CallableStatement cs, int columnIndex)
          throws SQLException {
        int value = cs.getInt(columnIndex);
        return forNumber(value);
      }
    
    }

自定义DateTime类型处理

package hander;
    
    import java.sql.CallableStatement;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Timestamp;
    import org.apache.ibatis.type.BaseTypeHandler;
    import org.apache.ibatis.type.JdbcType;
    import org.apache.ibatis.type.MappedJdbcTypes;
    import org.apache.ibatis.type.MappedTypes;
    
    /**
     * 数据类型转换从：代码中Long类型转到到Mysql中的datetime类型 pojo.Long->mysql.DateTime
     * 
     * @author KEVIN LUAN
     *
     */
    @MappedJdbcTypes(value = {JdbcType.TIMESTAMP})
    @MappedTypes({Long.class, long.class})
    public class DateTimeHander extends BaseTypeHandler<Long> {
      @Override
      public void setNonNullParameter(PreparedStatement ps, int i, Long parameter, JdbcType jdbcType)
          throws SQLException {
        ps.setTimestamp(i, new Timestamp(parameter));
      }
    
      @Override
      public Long getNullableResult(ResultSet rs, String columnName) throws SQLException {
        Timestamp timestamp = rs.getTimestamp(columnName);
        if (timestamp != null) {
          return timestamp.getTime();
        } else {
          return 0L;
        }
      }
    
      @Override
      public Long getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
        Timestamp timestamp = rs.getTimestamp(columnIndex);
        if (timestamp != null) {
          return timestamp.getTime();
        } else {
          return 0L;
        }
      }
    
      @Override
      public Long getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
        Timestamp timestamp = cs.getTimestamp(columnIndex);
        if (timestamp != null) {
          return timestamp.getTime();
        } else {
          return 0L;
        }
      }
    
    }

对象JSON 序列化类型

package hander;
    
    import java.sql.CallableStatement;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import org.apache.commons.lang3.StringUtils;
    import org.apache.ibatis.type.BaseTypeHandler;
    import org.apache.ibatis.type.JdbcType;
    import org.apache.ibatis.type.MappedJdbcTypes;
    import org.apache.ibatis.type.MappedTypes;
    import com.google.protobuf.GeneratedMessageV3;
    
    /**
     * 通用Proto Message转换处理
     * 
     * @author KEVIN LUAN
     *
     */
    @MappedJdbcTypes(value = {JdbcType.TINYINT})
    @MappedTypes({GeneratedMessageV3.class})
    public class JsonHander extends BaseTypeHandler<GeneratedMessageV3> {
      public Class<?> type;
    
      public JsonHander(Class<?> type) throws NoSuchMethodException, SecurityException {
        this.type = type;
      }
    
      public JsonHander() {}
    
      @Override
      public void setNonNullParameter(PreparedStatement ps, int i, GeneratedMessageV3 parameter,
          JdbcType jdbcType) throws SQLException {
        if (parameter != null) {
          String json = JacksonSerialize.INSTANCE.encode(parameter);
          ps.setString(i, json);
        } else {
          ps.setString(i, null);
        }
      }
    
      private GeneratedMessageV3 jsonAsBean(String value) {
        if (StringUtils.isNotBlank(value)) {
          return (GeneratedMessageV3) JacksonSerialize.INSTANCE.decode(value, type);
        }
        return null;
      }
    
      @Override
      public GeneratedMessageV3 getNullableResult(ResultSet rs, String columnName) throws SQLException {
        String value = rs.getString(columnName);
        return jsonAsBean(value);
      }
    
      @Override
      public GeneratedMessageV3 getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
        String value = rs.getString(columnIndex);
        return jsonAsBean(value);
      }
    
      @Override
      public GeneratedMessageV3 getNullableResult(CallableStatement cs, int columnIndex)
          throws SQLException {
        String value = cs.getString(columnIndex);
        return jsonAsBean(value);
      }
    
    }

在查询数据时使用ResultMap对属性指定对应的Hander即可例如

<resultMap type="model.XXXUser$Builder"
                   id="UserResultMap">
            <id column="id" property="id"/>
            
            <result column="create_time" property="createTime" typeHandler="hander.DateTimeHander"/>
            
        </resultMap>
    
    
      <insert id="saveBatch" parameterType="model.User$Builder" keyProperty="id_"
                useGeneratedKeys="true">
            <![CDATA[
    	INSERT INTO user 
    		(xx)
    		VALUES
    	]]>
            
           (#{item.createTime,typeHandler=hander.DateTimeHander})
        </insert>
    
    <select id="get" resultMap="UserResultMap">
    	<![CDATA[
    		SELECT * FROM user limit 1;
        ]]>
    </select>

到此 mybatis 支持proto就完成了。