Mybatis Plus 3.X版本的insert填充自增id的IdType.ID_WORKER策略源码分析

@Data
@AllArgsConstructor
@NoArgsConstructor
@ApiModel(value = "用户对象")
@TableName("user_info")
public class UserInfo {
    @ApiModelProperty(value = "用户ID", name = "id")
    @TableId(value = "id",type = IdType.ID_WORKER)
    private Integer id;
    @ApiModelProperty(value = "用户姓名", name = "userName")
    private String userName;
    @ApiModelProperty(value = "用户年龄", name = "age")
    private int age;
}

@Getter
public enum IdType {
    /**
     * 数据库ID自增
     */
    AUTO(0),
    /**
     * 该类型为未设置主键类型
     */
    NONE(1),
    /**
     * 用户输入ID
     * 该类型可以通过自己注册自动填充插件进行填充
     */
    INPUT(2),
​
    /* 以下3种类型、只有当插入对象ID 为空，才自动填充。 */
    /**
     * 全局唯一ID (idWorker)
     */
    ID_WORKER(3),
    /**
     * 全局唯一ID (UUID)
     */
    UUID(4),
    /**
     * 字符串全局唯一ID (idWorker 的字符串表示)
     */
    ID_WORKER_STR(5);
    
    ......
}

@Test
public void test(){
    UserInfo userInfo = new UserInfo();
    userInfo.setUserName("用户名");
    userInfo.setAge(1);
    userInfoMapper.insert(userInfo);
}

@Override
public int update(String statement, Object parameter) {
  try {
    dirty = true;
    MappedStatement ms = configuration.getMappedStatement(statement);
    return executor.update(ms, wrapCollection(parameter));
  } catch (Exception e) {
    throw ExceptionFactory.wrapException("Error updating database.  Cause: " + e, e);
  } finally {
    ErrorContext.instance().reset();
  }
}

public PreparedStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
  super(executor, mappedStatement, parameter, rowBounds, resultHandler, boundSql);
}

protected BaseStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
  this.configuration = mappedStatement.getConfiguration();
  this.executor = executor;
  this.mappedStatement = mappedStatement;
  this.rowBounds = rowBounds;
​
  this.typeHandlerRegistry = configuration.getTypeHandlerRegistry();
  this.objectFactory = configuration.getObjectFactory();
​
  if (boundSql == null) { // issue #435, get the key before calculating the statement
    generateKeys(parameterObject);
    boundSql = mappedStatement.getBoundSql(parameterObject);
  }
​
  this.boundSql = boundSql;
​
  this.parameterHandler = configuration.newParameterHandler(mappedStatement, parameterObject, boundSql);
  this.resultSetHandler = configuration.newResultSetHandler(executor, mappedStatement, rowBounds, parameterHandler, resultHandler, boundSql);
}

public ParameterHandler newParameterHandler(MappedStatement mappedStatement, Object parameterObject, BoundSql boundSql) {
  ParameterHandler parameterHandler = mappedStatement.getLang().createParameterHandler(mappedStatement, parameterObject, boundSql);
  parameterHandler = (ParameterHandler) interceptorChain.pluginAll(parameterHandler);
  return parameterHandler;
}

public class MybatisXMLLanguageDriver extends XMLLanguageDriver {
​
    @Override
    public ParameterHandler createParameterHandler(MappedStatement mappedStatement, Object parameterObject,
                                                   BoundSql boundSql) {
        /* 使用自定义 ParameterHandler */
        return new MybatisDefaultParameterHandler(mappedStatement, parameterObject, boundSql);
    }
}

public MybatisDefaultParameterHandler(MappedStatement mappedStatement, Object parameterObject, BoundSql boundSql) {
    super(mappedStatement, processBatch(mappedStatement, parameterObject), boundSql);
    this.mappedStatement = mappedStatement;
    this.configuration = mappedStatement.getConfiguration();
    this.typeHandlerRegistry = mappedStatement.getConfiguration().getTypeHandlerRegistry();
    this.parameterObject = parameterObject;
    this.boundSql = boundSql;
}

protected static Object populateKeys(MetaObjectHandler metaObjectHandler, TableInfo tableInfo,
                                     MappedStatement ms, Object parameterObject, boolean isInsert) {
    if (null == tableInfo) {
        /* 不处理 */
        return parameterObject;
    }
    /* 自定义元对象填充控制器 */
    MetaObject metaObject = ms.getConfiguration().newMetaObject(parameterObject);
    // 填充主键
    if (isInsert && !StringUtils.isEmpty(tableInfo.getKeyProperty())
        && null != tableInfo.getIdType() && tableInfo.getIdType().getKey() >= 3) {
        Object idValue = metaObject.getValue(tableInfo.getKeyProperty());
        /* 自定义 ID */
        if (StringUtils.checkValNull(idValue)) {
            if (tableInfo.getIdType() == IdType.ID_WORKER) {
                metaObject.setValue(tableInfo.getKeyProperty(), IdWorker.getId());
            } else if (tableInfo.getIdType() == IdType.ID_WORKER_STR) {
                metaObject.setValue(tableInfo.getKeyProperty(), IdWorker.getIdStr());
            } else if (tableInfo.getIdType() == IdType.UUID) {
                metaObject.setValue(tableInfo.getKeyProperty(), IdWorker.get32UUID());
            }
        }
    }
    if (metaObjectHandler != null) {
        if (isInsert && metaObjectHandler.openInsertFill()) {
            // 插入填充
            metaObjectHandler.insertFill(metaObject);
        } else if (!isInsert) {
            // 更新填充
            metaObjectHandler.updateFill(metaObject);
        }
    }
    return metaObject.getOriginalObject();
}