MyBatisPlus体验及使用

MyBatis 的增强版，但是我现在用的不多，JPA 为主

一、快速使用

• 1、编写 pojo

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private Long id;
    private String name;
    private Integer age;
    private String email;
}

• 2、SpringBoot 添加扫描包

@SpringBootApplication
@MapperScan("com.lqs.mybatisplusstart.mapper") //扫描mapper文件夹
public class MybatisplusstartApplication {
	public static void main(String[] args) {
		SpringApplication.run(MybatisplusstartApplication.class, args);
	}
}

• 3、编写 mapper 接口

/**
 * 继承基本的BaseMapper
 * 传入泛型
 */
public interface UserMapper extends BaseMapper<User> {
}

二、配置日志

mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

三、CRUD 扩展

1、自动填充

创建时间，修改时间，一般自动化完成

• alibaba 开发手册：gmt_created, gmt_modified 都必须有，需要自动

@TableField(fill = FieldFill.INSERT)
private LocalDateTime gmtCreated;
@TableField(fill = FieldFill.INSERT_UPDATE)
private LocalDateTime gmtModified;

编写处理器

@Slf4j
@Component
public class MyMetaObjectHandler implements MetaObjectHandler {
    //插入的更新策略
    @Override
    public void insertFill(MetaObject metaObject) {
        Log.info("start insert fill...");
        //String fieldName, Object fieldVal, MetaObject metaObject
        this.setFieldValByName("gmtCreated",  LocalDateTime.now(), metaObject);
    }
    //更新的策略
    @Override
    public void updateFill(MetaObject metaObject) {
        Log.info("start insert update fill...");
        this.setFieldValByName("gmtModified", LocalDateTime.now(), metaObject);
    }
}

2、乐/悲观锁

乐观锁：认为不会出现问题，做什么都不加锁。出现问题之后再次更新值测试

悲观锁：认为会出现问题，干什么都上锁，再去操作

实体类增加对应的字段

@Version //乐观锁注解
private Integer version;

注册组件

@EnableTransactionManagement
 //扫描mapper文件夹,将主类的配置拿到此处
@MapperScan("com.lqs.mybatisplusstart.mapper")
@Configuration
public class MybatisPlusConfig {
    @Bean //注册乐观锁插件
    public OptimisticLockerInterceptor optimisticLockerInterceptor(){
        return new OptimisticLockerInterceptor();
    }
}

3、逻辑删除

• 例子：管理员可以查看被删除的东西，普通用户不可以,增加 deleted 字段
• 增加配置

@Bean
    public ISqlInjector sqlInjector(){
        return new LogicSqlInjector();
    }

mybatis-plus:
  global-config:
    db-config:
      #逻辑删除
      logic-delete-value: 1
      logic-not-delete-value: 0

4、批量插入/批量插入或更新

• 批量插入或更新插件

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.core.injector.AbstractMethod;
import com.baomidou.mybatisplus.core.metadata.TableFieldInfo;
import com.baomidou.mybatisplus.core.metadata.TableInfo;
import com.baomidou.mybatisplus.core.metadata.TableInfoHelper;
import com.baomidou.mybatisplus.core.toolkit.sql.SqlInjectionUtils;
import com.baomidou.mybatisplus.core.toolkit.sql.SqlScriptUtils;
import lombok.Setter;
import lombok.experimental.Accessors;
import org.apache.ibatis.executor.keygen.Jdbc3KeyGenerator;
import org.apache.ibatis.executor.keygen.KeyGenerator;
import org.apache.ibatis.executor.keygen.NoKeyGenerator;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.SqlSource;

import java.util.List;
import java.util.function.Predicate;

/**
 * <p>
 * 批量插入或更新
 * </p>
 * @since 3.5.0
 * @author aries
 */
@Setter
public class InsertOrUpdateBatch extends AbstractMethod {
    private static final String NAME = "insertOrUpdateBatch";
    /**
     * 字段筛选条件
     */
    @Accessors(chain = true)
    private Predicate<TableFieldInfo> predicate;

    /**
     * 默认方法名
     */
    public InsertOrUpdateBatch() {
        super(NAME);
    }

    /**
     * 默认方法名
     *
     * @param predicate 字段筛选条件
     */
    public InsertOrUpdateBatch(Predicate<TableFieldInfo> predicate) {
        super(NAME);
        this.predicate = predicate;
    }

    /**
     * @param name      方法名
     * @param predicate 字段筛选条件
     * @since 3.5.0
     */
    public InsertOrUpdateBatch(String name, Predicate<TableFieldInfo> predicate) {
        super(name);
        this.predicate = predicate;
    }

    @SuppressWarnings("Duplicates")
    @Override
    public MappedStatement injectMappedStatement(Class<?> mapperClass, Class<?> modelClass, TableInfo tableInfo) {
        KeyGenerator keyGenerator = NoKeyGenerator.INSTANCE;
        String methodSql = """
                <script>
                INSERT INTO %s %s VALUES %s  ON DUPLICATE KEY UPDATE %s
                </script>""";
        List<TableFieldInfo> fieldList = tableInfo.getFieldList();
        String insertSqlColumn = tableInfo.getKeyInsertSqlColumn(true, null, false) +
                this.filterTableFieldInfo(fieldList, predicate, TableFieldInfo::getInsertSqlColumn, EMPTY);
        String columnScript = LEFT_BRACKET + insertSqlColumn.substring(0, insertSqlColumn.length() - 1) + RIGHT_BRACKET;
        String insertSqlProperty = tableInfo.getKeyInsertSqlProperty(true, ENTITY_DOT, false) +
                this.filterTableFieldInfo(fieldList, predicate, i -> i.getInsertSqlProperty(ENTITY_DOT), EMPTY);
        String valueUpdateScript = this.filterTableFieldInfo(fieldList, predicate, f -> {
            String s = f.getInsertSqlColumn().replace(",", "");
            return String.format("%s =values(%s)", s, s);
        }, ",");
        insertSqlProperty = LEFT_BRACKET + insertSqlProperty.substring(0, insertSqlProperty.length() - 1) + RIGHT_BRACKET;
        String valuesScript = SqlScriptUtils.convertForeach(insertSqlProperty, "list", null, ENTITY, COMMA);
        String keyProperty = null;
        String keyColumn = null;
        // 表包含主键处理逻辑,如果不包含主键当普通字段处理
        if (tableInfo.havePK()) {
            if (tableInfo.getIdType() == IdType.AUTO) {
                /* 自增主键 */
                keyGenerator = Jdbc3KeyGenerator.INSTANCE;
                keyProperty = tableInfo.getKeyProperty();
                // 去除转义符
                keyColumn = SqlInjectionUtils.removeEscapeCharacter(tableInfo.getKeyColumn());
            } else {
                if (null != tableInfo.getKeySequence()) {
                    keyGenerator = TableInfoHelper.genKeyGenerator(this.methodName, tableInfo, builderAssistant);
                    keyProperty = tableInfo.getKeyProperty();
                    keyColumn = tableInfo.getKeyColumn();
                }
            }
        }
        String sql = String.format(methodSql, tableInfo.getTableName(), columnScript, valuesScript,valueUpdateScript);
        SqlSource sqlSource = super.createSqlSource(configuration, sql, modelClass);
        return this.addInsertMappedStatement(mapperClass, modelClass, methodName, sqlSource, keyGenerator, keyProperty, keyColumn);
    }
}

• 添加并注入 injector

import com.baomidou.mybatisplus.annotation.FieldFill;
import com.baomidou.mybatisplus.core.injector.AbstractMethod;
import com.baomidou.mybatisplus.core.injector.DefaultSqlInjector;
import com.baomidou.mybatisplus.core.metadata.TableInfo;
import com.baomidou.mybatisplus.extension.injector.methods.InsertBatchSomeColumn;

import java.util.List;

public class MySqlInjector extends DefaultSqlInjector {

    @Override
    public List<AbstractMethod> getMethodList(Class<?> mapperClass, TableInfo tableInfo) {
        List<AbstractMethod> methodList = super.getMethodList(mapperClass, tableInfo);
        //这是mybatisplus自带的批量插入方法
        methodList.add(new InsertBatchSomeColumn(i -> i.getFieldFill() != FieldFill.UPDATE));
        methodList.add(new InsertOrUpdateBatch());
        return methodList;
    }
}

    @Bean
    public MySqlInjector sqlInjector() {
        return new MySqlInjector();
    }