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Fluent API

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Prerequisites​

Before using LambdaTemplate, prepare a data source just like you would for JdbcTemplate. You can also pass an existing JdbcTemplate into the LambdaTemplate constructor to share the same database connection.

  • Ensure you have object mappings for the database tables you operate on.
  • Annotations are one way to configure mappings; see Object Mapping for more options and details.
1. Create an object mapping for the users table via annotations
@Table("users")
public class User {
    @Column(name = "id", primary = true, keyType = KeyTypeEnum.Auto)
    private Long id;
    @Column("name")
    private String name;
    ... // getters/setters omitted
}
  • @Table marks the type as an entity and sets the table name it maps to.
  • @Column defines the mapping between fields and columns.
  • In the example, id is marked as the primary key and is auto-incremented by the database.
2. Create the builder
DataSource dataSource = ...;
LambdaTemplate lambda = new LambdaTemplate(dataSource);

// or

Connection conn = ...;
LambdaTemplate lambda = new LambdaTemplate(conn);
  • Use the methods on lambda to perform reads and writes.
  • By default, LambdaTemplate uses RegistryManager.DEFAULT to manage type mappings.

How It Works​

LambdaTemplate provides insert, update, delete, query, and freedom methods to operate on tables:

  • insert generates and executes INSERT statements.
  • update generates and executes UPDATE statements.
  • delete generates and executes DELETE statements.
  • query generates and executes SELECT statements.

You describe how to build SQL and arguments in code; at runtime the SQL is generated and executed through JdbcTemplate to return results.

Guide​

  • Insert: write data, batch for efficiency, and handle conflicts.
  • Update: three update methods and how to avoid unsafe updates.
  • Delete: delete data with LambdaTemplate.
  • Query: query data with the constructor APIs provided by dbVisitor.
  • Where builder: build rich conditions for update, delete, and query.
  • Group by: perform grouped queries.
  • Order by: apply ordering to queries.
  • Map APIs: Map remains a handy container alongside entity classes.
  • Freedom mode: build and execute SQL with Maps even without mapped entity classes.