基于Mybatis-Plus实现DuplicateKeyUpdateMapper

• 参考Mybatis-Plus方法生成策略（com.baomidou.mybatisplus.core.injector.methods.Update）

• 参考MySQL的INSERT INTO ON DUPLICATE KEY UPDATE语法

• 生成动态SQL脚本模板

CREATE TABLE `test_entity`
(
    `id`   int(11) NOT NULL AUTO_INCREMENT,
    `name` varchar(20) DEFAULT NULL,
    `age`  int(11)     DEFAULT NULL,
    PRIMARY KEY (`id`)
) ENGINE = InnoDB
  DEFAULT CHARSET = utf8mb4

@Data
public class TestEntity {
    
    @TableId
    private Integer id;
    
    private String name;
    
    private Integer age;
}

• 注意需要继承BaseMapper

public interface DuplicateKeyUpdateMapper extends BaseMapper {

    
    int duplicateKeyUpdate(List list);

}

public class DuplicateKeyUpdateMethod extends AbstractMethod {

    @Override
    public MappedStatement injectMappedStatement(Class mapperClass, Class modelClass, TableInfo tableInfo) {
        //脚本模板
        String sql = "";
        //字段list（除了主键）
        List fieldList = tableInfo.getFieldList();
        //全部字段
        List allFieldName = fieldList.stream()
                .map(TableFieldInfo::getColumn)
                .collect(Collectors.toList());
        allFieldName.add(0, tableInfo.getKeyColumn());

        //生成所需的sql片段
        String fieldNames = String.join(", ", allFieldName);
        String insertFields = allFieldName.stream()
                .map(field -> "#{item." + field + "}")
                .collect(Collectors.joining(", "));
        insertFields = "(" + insertFields + ")";
        String updateFields = fieldList.stream()
                .map(field -> {
                    String column = field.getColumn();
                    return column + "=values(" + column + ")";
                })
                .collect(Collectors.joining(",n"));

        //生成具体脚本
        String sqlResult = String.format(sql, tableInfo.getTableName(), fieldNames, insertFields, updateFields);
        SqlSource sqlSource = languageDriver.createSqlSource(configuration, sqlResult, modelClass);
        return this.addUpdateMappedStatement(mapperClass, modelClass, "duplicateKeyUpdate", sqlSource);
    }

}

public class MyBatisPlusConfig {

    @Bean
    public DefaultSqlInjector myLogicSqlInjector() {
        return new DefaultSqlInjector() {
            @Override
            public List getMethodList(Class mapperClass) {
                List methodList = super.getMethodList(mapperClass);
                methodList.add(new DuplicateKeyUpdateMethod());
                return methodList;
            }
        };
    }
}