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mybatis查询默认是一次获取全部， 有时候需要查询上万上百万数据时，如果一次性读取到内存中，会容易导致OOM问题。这时候需要采用流式查询。以下扩展了tk.mybatis的流式查询
mybatis查询默认是一次获取全部， 有时候需要查询上万上百万数据时，如果一次性读取到内存中，会容易导致OOM问题。这时候需要采用流式查询。以下扩展了tk.mybatis的流式查询功能。 直接上干货：
@Options注解是关键
import org.apache.ibatis.annotations.Options;
import org.apache.ibatis.annotations.SelectProvider;
import org.apache.ibatis.mapping.ResultSetType;
import org.apache.ibatis.session.ResultHandler;
@tk.mybatis.mapper.annotation.ReGISterMapper
public interface SelectStreamByExampleMapper<T> {
@Options(resultSetType = ResultSetType.FORWARD_ONLY, fetchSize = 1000)
@SelectProvider(type = StreamExampleProvider.class, method = "dynamicsql")
void selectStreamByExampleMapper(Object example, ResultHandler resultHandler);
}带RowBounds的流式查询
import org.apache.ibatis.annotations.Options;
import org.apache.ibatis.annotations.SelectProvider;
import org.apache.ibatis.mapping.ResultSetType;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
@tk.mybatis.mapper.annotation.RegisterMapper
public interface SelectStreamByExampleRowBoundsMapper<T> {
@Options(resultSetType = ResultSetType.FORWARD_ONLY, fetchSize = 1000)
@SelectProvider(type = StreamExampleProvider.class, method = "dynamicSQL")
void selectStreamByExampleRowBoundsMapper(Object example, RowBounds rowBounds, ResultHandler resultHandler);
}流式ExampleProvider
import org.apache.ibatis.mapping.MappedStatement;
import tk.mybatis.mapper.mapperhelper.MapperHelper;
import tk.mybatis.mapper.provider.ExampleProvider;
public class StreamExampleProvider extends ExampleProvider {
public StreamExampleProvider(Class<?> mapperClass, MapperHelper mapperHelper) {
super(mapperClass, mapperHelper);
}
public String selectStreamByExampleMapper(MappedStatement ms) {
return this.selectByExample(ms);
}
public String selectStreamByExampleRowBoundsMapper(MappedStatement ms) {
return this.selectByExample(ms);
}
}将SelectStreamByExampleMapper和SelectStreamByExampleRowBoundsMapper组合成一个接口
@tk.mybatis.mapper.annotation.RegisterMapper
public interface StreamMapper<T> extends
SelectStreamByExampleMapper<T>,
SelectStreamByExampleRowBoundsMapper<T> {
}
在BaseMapper中加入StreamMapper
public interface BaseMapper<T> extends Mapper<T>, MysqlMapper<T>, StreamMapper<T> {
}使用例子：
this.userMapper.selectStreamByExampleRowBoundsMapper(example, new RowBounds(0, 1), resultContext -> {
User user= (User) resultContext.getResultObject();
System.out.println(user);
});
this.userMapper.selectStreamByExampleMapper(example, resultContext -> {
User user= (User) resultContext.getResultObject();
System.out.println(User);
});到此这篇关于扩展tk.mybatis的流式查询功能实现的文章就介绍到这了,更多相关tk.mybatis 流式查询内容请搜索编程网以前的文章或继续浏览下面的相关文章希望大家以后多多支持编程网！
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本文标题: 扩展tk.mybatis的流式查询功能实现
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