扩展tk.mybatis的流式查询功能实现

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;

/**
 * 通用mapper接口,流式查询
 *
 * @param <t> 不能为空
 * @author sunchangtan
 */
@tk.mybatis.mapper.annotation.registermapper
public interface selectstreambyexamplemapper<t> {

    /**
     * 根据example条件和rowbounds进行流式查询
     *
     * @param example
     * @return
     */
    @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;

/**
 * 通用mapper接口,流式查询
 *
 * @param <t> 不能为空
 * @author sunchangtan
 */
@tk.mybatis.mapper.annotation.registermapper
public interface selectstreambyexamplerowboundsmapper<t> {

    /**
     * 根据example条件和rowbounds进行流式查询
     *
     * @param example
     * @return
     */
    @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;

/**
 * 流式查询的sqlprovider
 * @author sunchangtan
 */

public class streamexampleprovider extends exampleprovider {

    public streamexampleprovider(class<?> mapperclass, mapperhelper mapperhelper) {
        super(mapperclass, mapperhelper);
    }


    /**
     * 根据example流式查询
     *
     * @param ms
     * @return
     */
    public string selectstreambyexamplemapper(mappedstatement ms) {
        return this.selectbyexample(ms);
    }

    /**
     * 根据example和rowbounds流式查询
     * @param ms
     * @return
     */
    public string selectstreambyexamplerowboundsmapper(mappedstatement ms) {
        return this.selectbyexample(ms);
    }

}

将selectstreambyexamplemapper和selectstreambyexamplerowboundsmapper组合成一个接口

/**
 * 流式查询接口
 * @param <t>
 * @author sunchangtan
 */
@tk.mybatis.mapper.annotation.registermapper
public interface streammapper<t> extends
        selectstreambyexamplemapper<t>,
        selectstreambyexamplerowboundsmapper<t> {
}

在basemapper中加入streammapper

/**
 * mapper的基类
 * @author sunchangtan
 * @param <t>
 */
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);
});

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