1. Fluent Chain APIs (Deep Dive)

While helper methods like .query(), .update(), and .insert() cover common use cases, Chain APIs provide granular control over the execution process. They allow you to build complex SQL commands step-by-step before executing them.

You access these chains via the DataManager (or BaseService which delegates to it).

1.1 QueryChain

The QueryChain offers the most flexibility for data retrieval, allowing precise control over selected columns, joins, and sorting.

Entry Point: dataManager.queryChain()

List<User> users = userService.queryChain()
    // 1. Select specific columns (SQL optimization)
    .select(User.Fields.id, User.Fields.name, "department.name") 

    // 2. Add Joins manually (if not using automatic @ToOne/@ToMany inference)
    .join(Join.inner("department")
              .on(c -> c.eq("active", true)))

    // 3. Filtering
    .where(c -> c.gt(User.Fields.age, 18))

    // 4. Sorting
    .asc(User.Fields.age)      // Order by age ASC
    .desc(User.Fields.createTime) // Then by create_time DESC

    // 5. Execute
    .exec();

• .select(String... fields): Restricts the columns fetched from the database. Can include fields from joined tables (e.g., "department.name").
• .joins(Join...): Explicitly defines joins. Useful when you need specific join types (INNER, LEFT) or extra conditions on the JOIN clause itself.
• .ignoreLogicDelete(): If your model uses logical deletion, this forces the query to include deleted records.

1.2 UpdateChain

The UpdateChain allows you to customize how updates are applied, specifically regarding null values and "force" updates.

Entry Point: dataManager.updateChain()

userService.updateChain()
    .id(userId)
    .data(userObj)

    // Strategy: Only update fields that are NOT NULL in 'userObj'
    .updateOnlyNonNull() 

    // Strategy: Force update even if data hasn't changed 
    // (useful to update 'updateTime' or version columns)
    .force()

    // Strategy: Explicitly ignore certain fields even if they are set
    .ignoreFields(User.Fields.password, User.Fields.salt)

    .exec();

• .updateOnlyNonNull(): By default, update might overwrite database values with null if the field in the provided object is null. This method prevents that.
• .allowNull() (Implicit default): The opposite of updateOnlyNonNull.
• .force(): Standard updates check if values actually changed to avoid unnecessary DB writes. .force() bypasses this check.

1.3 PageChain

Combines standard query capabilities with pagination.

Entry Point: dataManager.pageChain()

PageResult<User> page = userService.pageChain()
    .page(1, 20) // Current Page, Page Size
    .where(c -> c.eq("status", "ACTIVE"))
    .desc(User.Fields.createTime)
    .exec();

// Result contains:
long total = page.getTotal();
List<User> list = page.getData();

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