Connection Manager

Concept

In Jimmer, all executable statements and instructions support two execution modes:

• Execute based on the JDBC connection specified by the user

• Executed by Jimmer automatically determining based on a JDBC connection

Here, take Executable (Java) or KExecutable (Kotlin) interface as an example

Java

Executable.java

package org.babyfish.jimmer.sql.ast;

import java.sql.Connection;

public interface Executable<R> {

    R execute();

    R execute(Connection con);
}

Kotlin

KExecutable.kt

package org.babyfish.jimmer.sql.kt

import java.sql.Connection  

interface KExecutable<R> {
  fun execute(con: Connection? = null): R
}

• execute(Connection): Execute on the JDBC connection specified by the user.

  Take query as an example:

  Java

  BookTable book = Tables.BOOK_TABLE;
  
  List<Book> books = sqlClient
      .createQuery(book)
      .select(book)
      .execute(con);

  Kotlin

  val books = sqlClient
      .createQuery(Book::class) {
          select(table)
      }
      .execute(con)
  info

  For this usage, no special configuration of SqlClient is required.

• execute() or execute(null): Determined by Jimmer to execute on a JDBC connection.

  Take query as an example:

  Java

  BookTable book = Tables.BOOK_TABLE;
  
  List<Book> books = sqlClient
      .createQuery(book)
      .select(book)
      .execute();

  Kotlin

  val books = sqlClient
      .createQuery(Book::class) {
          select(table)
      }
      .execute()
  info

  For this usage, ConnectionManager must be configured for SqlClient. Otherwise it will cause exceptions.

  Undoubtedly, the 2nd approach is more in line with the requirements of business system development, so it is recommended. So it is strongly recommended to configure ConnectionManager for SqlClient.

Simple ConnectionManager

Java

javax.sql.DataSource dataSource = ...;

JSqlClient sqlClient = JSqlClient
    .newBuilder()
    .setConnectionManager(
        ConnectionManager
        .simpleConnectionManager(dataSource)
    )
    .build(); 

Kotlin

val dataSource: javax.sql.DataSource = ...

val sqlClient = newKSqlClient {
    setConnectionManager {
        dataSource.connection.use {
            proceed(it)
        }
    }
}

danger

This way is only responsible for getting connections from DataSource and has no transaction management mechanism.

However, transactions are very important in actual projects. Therefore, except for learning and trying, it is not recommended to use this approach in actual projects.

ConnectionManager managed by Spring transaction

This topic has been discussed in detail in Spring Section/Integrate Spring Transaction. This article will not repeat the explanation.

tip

Letting Jimmer be managed by Spring transaction is the recommended usage.