Mybatis自定义Mapper和MapperTemplate实现通用sql

最近项目中开始对接阿里开源的seata分布式事务框架，对接的时候使用update更新数据库记录的时候，应用出现了报错update pk value is not supported!，意思是我使用的tk.mybatis.mapper框架中的updateByExampleSelective等一系列的update语句均会对id进行更新操作，如：

update tableName set id=id, ...

网上查询资料，决定自定义update的通用方法来解决这个问题。

自定义provider

首先新建一个类来生成对应的update语句。
其中包含了4个update方法：

1. updateByPrimaryKeySpecial对应updateByPrimaryKey方法
2. updateByPrimaryKeySelectiveSpecial对应updateByPrimaryKeySelective方法
3. updateByExampleSelectiveSpecial对应updateByExampleSelective
4. updateByExampleSpecial对应updateByExample方法

package com.gugu.core.mybatis.provider;

import com.gugu.core.mybatis.mapperhelper.SqlHelper;
import org.apache.ibatis.mapping.MappedStatement;
import tk.mybatis.mapper.mapperhelper.MapperHelper;
import tk.mybatis.mapper.mapperhelper.MapperTemplate;

/**
 * 特殊的更新.
 * <p/>
 * SpecialUpdateProvider
 *
 * @author zhoumeiqin
 * @date 2020/11/17
 */
public class SpecialUpdateProvider extends MapperTemplate {
    public SpecialUpdateProvider(Class<?> mapperClass, MapperHelper mapperHelper) {
        super(mapperClass, mapperHelper);
    }

    public String updateByPrimaryKeySpecial(MappedStatement ms) {
        Class<?> entityClass = this.getEntityClass(ms);
        StringBuilder sql = new StringBuilder();
        sql.append(SqlHelper.updateTable(entityClass, this.tableName(entityClass)));
        sql.append(SqlHelper.updateSetColumns(entityClass, (String)null, false, false));
        sql.append(SqlHelper.wherePKColumns(entityClass, true));
        return sql.toString();
    }

    public String updateByPrimaryKeySelectiveSpecial(MappedStatement ms) {
        Class<?> entityClass = this.getEntityClass(ms);
        StringBuilder sql = new StringBuilder();
        sql.append(SqlHelper.updateTable(entityClass, this.tableName(entityClass)));
        sql.append(SqlHelper.updateSetColumns(entityClass, (String)null, true, this.isNotEmpty()));
        sql.append(SqlHelper.wherePKColumns(entityClass, true));
        return sql.toString();
    }

    public String updateByExampleSelectiveSpecial(MappedStatement ms) {
        Class<?> entityClass = this.getEntityClass(ms);
        StringBuilder sql = new StringBuilder();
        if (this.isCheckExampleEntityClass()) {
            sql.append(SqlHelper.exampleCheck(entityClass));
        }

        if (this.getConfig().isSafeUpdate()) {
            sql.append(SqlHelper.exampleHasAtLeastOneCriteriaCheck("example"));
        }

        sql.append(SqlHelper.updateTable(entityClass, this.tableName(entityClass), "example"));
        sql.append(SqlHelper.updateSetColumns(entityClass, "record", true, this.isNotEmpty()));
        sql.append(SqlHelper.updateByExampleWhereClause());
        return sql.toString();
    }

    public String updateByExampleSpecial(MappedStatement ms) {
        Class<?> entityClass = this.getEntityClass(ms);
        StringBuilder sql = new StringBuilder();
        if (this.isCheckExampleEntityClass()) {
            sql.append(SqlHelper.exampleCheck(entityClass));
        }
        if (this.getConfig().isSafeUpdate()) {
            sql.append(SqlHelper.exampleHasAtLeastOneCriteriaCheck("example"));
        }
        sql.append(SqlHelper.updateTable(entityClass, this.tableName(entityClass), "example"));
        sql.append(SqlHelper.updateSetColumns(entityClass, "record", false, false));
        sql.append(SqlHelper.updateByExampleWhereClause());
        return sql.toString();
    }
}

这里因为场景问题，这里copy了一份mybatis中的SqlHelper中的代码
只修改了updateSetColumns()的方法中对于主键的更新处理

if (!column.isId() && column.isUpdatable()) {
    if (column == versionColumn) {
        Version version = (Version) versionColumn.getEntityField().getAnnotation(Version.class);
        String versionClass = version.nextVersion().getCanonicalName();
        sql.append(column.getColumn()).append(" = ${@tk.mybatis.mapper.version.VersionUtil@nextVersion(\"").append(versionClass).append("\", ").append(column.getProperty()).append(")},");
    } else if (notNull) {
        sql.append(getIfNotNull(entityName, column, column.getColumnEqualsHolder(entityName) + ",", notEmpty));
    } else {
        sql.append(column.getColumnEqualsHolder(entityName) + ",");
    }
} else if (column.isId()) {
    // update 语句不应该修改主键信息
    // sql.append(column.getColumn()).append(" = ").append(column.getColumn()).append(",");
}

新建自定义Mapper

package com.gugu.core.mybatis.mapper;

import com.gugu.core.mybatis.provider.SpecialUpdateProvider;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.UpdateProvider;
import tk.mybatis.mapper.annotation.RegisterMapper;

/**
 * 特殊的更新.
 * <p/>
 * SpecialUpdateMapper
 *
 * @author zhoumeiqin
 * @date 2020/11/17
 */
@RegisterMapper
public interface SpecialUpdateMapper<T> {

    @UpdateProvider(type = SpecialUpdateProvider.class, method = "dynamicSQL")
    int updateByPrimaryKeySpecial(T var1);

    @UpdateProvider(type = SpecialUpdateProvider.class, method = "dynamicSQL")
    int updateByPrimaryKeySelectiveSpecial(T var1);

    @UpdateProvider(type = SpecialUpdateProvider.class, method = "dynamicSQL")
    int updateByExampleSelectiveSpecial(@Param("record") T var1, @Param("example") Object var2);

    @UpdateProvider(type = SpecialUpdateProvider.class, method = "dynamicSQL")
    int updateByExampleSpecial(@Param("record") T var1, @Param("example") Object var2);
}

SpringBoot中配置

Mybatis默认只支持tk.mybatis.mapper.common.Mapper，会报错误。

Error invoking SqlProvider method (tk.mybatis.mapper.provider.SpecialProvider.dynamicSQL)
java.lang.NoSuchMethodException: tk.mybatis.mapper.provider.SpecialProvider.<init>()