Merge pull request #3745 from ebean-orm/docs/guides-one

rob-bygrave · web-flow · commit af443ef2f2bd · 2026-04-10T23:42:33.000+12:00
Docs: Add docs / guides for step-by-step instructions for AI agents
diff --git a/README.md b/README.md
@@ -81,6 +81,9 @@ or [github discussions](https://github.com/ebean-orm/ebean/discussions)
 ## Documentation
 Goto [https://ebean.io/docs/](https://ebean.io/docs/)
 
+## Guides
+Step-by-step guides for common tasks: [docs/guides/](docs/guides/README.md)
+
 ## Maven central
 [Maven central - g:io.ebean](http://search.maven.org/#search%7Cgav%7C1%7Cg%3A%22io.ebean%22%20)
 
diff --git a/docs/guides/README.md b/docs/guides/README.md
@@ -0,0 +1,13 @@
+# Guides
+
+Step-by-step guides written as instructions for AI agents and developers.
+
+## Adding Ebean ORM with PostgreSQL to an existing Maven project
+
+A two-part guide covering everything needed to wire Ebean + PostgreSQL into an
+existing Maven project. Complete the steps in order.
+
+| Step | Guide | Description |
+|------|-------|-------------|
+| 1 | [Maven POM setup](add-ebean-postgres-maven-pom.md) | Add Ebean dependencies, the enhancement plugin, and the querybean-generator annotation processor to `pom.xml` |
+| 2 | [Database configuration](add-ebean-postgres-database-config.md) | Configure the Ebean `Database` bean using `DataSourceBuilder` and `DatabaseConfig` with Avaje Inject |
diff --git a/docs/guides/add-ebean-postgres-database-config.md b/docs/guides/add-ebean-postgres-database-config.md
@@ -0,0 +1,211 @@
+# Guide: Add Ebean ORM (PostgreSQL) to an Existing Maven Project — Step 2: Database Configuration
+
+## Purpose
+
+This guide provides step-by-step instructions for configuring an Ebean `Database` bean
+using **Avaje Inject** (`@Factory` / `@Bean`), backed by a PostgreSQL datasource built
+with Ebean's `DataSourceBuilder`. Follow every step in order. This is Step 2 of 2.
+
+---
+
+## Prerequisites
+
+- **Step 1 complete**: `pom.xml` already includes `ebean-postgres`, `ebean-maven-plugin`,
+  and `querybean-generator` (see `add-ebean-postgres-maven-pom.md`)
+- **Avaje Inject** is on the classpath (e.g. `io.avaje:avaje-inject`)
+- A configuration source is available at runtime (e.g. `avaje-config` reading
+  `application.yml` or environment variables)
+- The following configuration keys are resolvable at runtime (adapt names to your project):
+  | Key | Description |
+  |-----|-------------|
+  | `db_url` | JDBC URL for the master/write connection |
+  | `db_user` | Database username |
+  | `db_pass` | Database password |
+  | `db_master_min_connections` | Minimum pool size (default: 1) |
+  | `db_master_max_connections` | Maximum pool size (default: 200) |
+
+---
+
+## Step 1 — Locate or create the `@Factory` class
+
+Look for an existing Avaje Inject `@Factory`-annotated class in the project
+(often named `AppConfig`, `DatabaseConfig`, or similar). If one exists, add the new
+`@Bean` method to it. If none exists, create one:
+
+```java
+package com.example.configuration;
+
+import io.avaje.inject.Bean;
+import io.avaje.inject.Factory;
+
+@Factory
+class DatabaseConfig {
+    // beans will be added in the steps below
+}
+```
+
+---
+
+## Step 2 — Add the `Database` bean method (minimal — master datasource only)
+
+Add the following `@Bean` method to the `@Factory` class. This creates an Ebean
+`Database` backed by a single master (read-write) PostgreSQL datasource.
+
+```java
+import io.ebean.Database;
+import io.ebean.config.DatabaseConfig;
+import io.ebean.datasource.DataSourceBuilder;
+
+@Bean
+Database database() {
+    var dataSource = DataSourceBuilder.create()
+        .url(/* resolve from config, e.g.: */ Config.get("db_url"))
+        .username(Config.get("db_user"))
+        .password(Config.get("db_pass"))
+        .driver("org.postgresql.Driver")
+        .schema("myschema")                    // set to your target schema
+        .applicationName("my-app")             // visible in pg_stat_activity
+        .minConnections(Config.getInt("db_master_min_connections", 1))
+        .maxConnections(Config.getInt("db_master_max_connections", 200));
+
+    return new DatabaseConfig()
+        .name("db")                            // logical name for this Database instance
+        .dataSourceBuilder(dataSource)
+        .build();
+}
+```
+
+### Field guidance
+
+| Field | Notes |
+|-------|-------|
+| `url` | Full JDBC URL, e.g. `jdbc:postgresql://host:5432/dbname` |
+| `schema` | The Postgres schema Ebean should use (omit if using `public`) |
+| `applicationName` | Shown in `pg_stat_activity.application_name`; helps with DB-side diagnostics |
+| `name("db")` | Logical Ebean database name; relevant if multiple Database instances exist |
+
+---
+
+## Step 3 — Inject configuration via a constructor or config helper (recommended)
+
+Rather than calling `Config.get(...)` inline, inject a typed config helper or the
+Avaje `Configuration` bean if one is available. This makes the factory testable and
+keeps the wiring explicit. For example:
+
+```java
+@Bean
+Database database(Configuration config) {
+    String url  = config.get("db_url");
+    String user = config.get("db_user");
+    String pass = config.get("db_pass");
+    int    min  = config.getInt("db_master_min_connections", 1);
+    int    max  = config.getInt("db_master_max_connections", 200);
+
+    var dataSource = DataSourceBuilder.create()
+        .url(url)
+        .username(user)
+        .password(pass)
+        .driver("org.postgresql.Driver")
+        .schema("myschema")
+        .applicationName("my-app")
+        .minConnections(min)
+        .maxConnections(max);
+
+    return new DatabaseConfig()
+        .name("db")
+        .dataSourceBuilder(dataSource)
+        .skipDataSourceCheck(true)
+        .build();
+}
+```
+
+If the project has a dedicated config-wrapper class (a `@Component` that reads config
+keys), accept it as a parameter instead of `Configuration`.
+
+---
+
+## Step 4 (Optional) — Add a read-only datasource
+
+For production services that have a separate read-replica, add a second
+`DataSourceBuilder` for read-only queries and wire it via
+`readOnlyDataSourceBuilder(...)`. The read-only datasource:
+
+- Uses `readOnly(true)` and `autoCommit(true)` (Ebean routes read queries there automatically)
+- Typically has a higher max connection count than the master
+- Benefits from a prepared-statement cache (`pstmtCacheSize`)
+
+```java
+@Bean
+Database database(Configuration config) {
+    String masterUrl   = config.get("db_url");
+    String readOnlyUrl = config.get("db_url_readonly");
+    String user        = config.get("db_user");
+    String pass        = config.get("db_pass");
+
+    var masterDataSource = buildDataSource(user, pass)
+        .url(masterUrl)
+        .minConnections(config.getInt("db_master_min_connections", 1))
+        .maxConnections(config.getInt("db_master_max_connections", 50));
+
+    var readOnlyDataSource = buildDataSource(user, pass)
+        .url(readOnlyUrl)
+        .readOnly(true)
+        .autoCommit(true)
+        .pstmtCacheSize(250)          // cache up to 250 prepared statements per connection
+        .maxInactiveTimeSecs(600)     // close idle connections after 10 minutes
+        .minConnections(config.getInt("db_readonly_min_connections", 2))
+        .initialConnections(config.getInt("db_readonly_initial_connections", 10))
+        .maxConnections(config.getInt("db_readonly_max_connections", 200));
+
+    return new DatabaseConfig()
+        .name("db")
+        .dataSourceBuilder(masterDataSource)
+        .readOnlyDataSourceBuilder(readOnlyDataSource)
+        .build();
+}
+
+private static DataSourceBuilder buildDataSource(String user, String pass) {
+    return DataSourceBuilder.create()
+        .username(user)
+        .password(pass)
+        .driver("org.postgresql.Driver")
+        .schema("myschema")
+        .applicationName("my-app")
+        .addProperty("prepareThreshold", "2");   // PostgreSQL: server-side prepared statements
+}
+```
+
+### Additional configuration keys for the read-only datasource
+
+| Key | Description | Default |
+|-----|-------------|---------|
+| `db_url_readonly` | JDBC URL for the read replica | — |
+| `db_readonly_min_connections` | Minimum pool size | 2 |
+| `db_readonly_initial_connections` | Initial pool size at startup | same as min |
+| `db_readonly_max_connections` | Maximum pool size | 20 |
+
+---
+
+## Verification
+
+1. Start the application (or run `mvn test -pl <your-module>`).
+2. Look for log output similar to:
+
+   ```
+   INFO  o.a.datasource.pool.ConnectionPool - DataSourcePool [db] autoCommit[false] min[1] max[5]
+   INFO  io.ebean.internal.DefaultContainer - DatabasePlatform name:db platform:postgres
+   ```
+
+3. If you see `DataSourcePool` and `DatabasePlatform` log lines, Ebean is connected and
+   the database bean is wired correctly.
+
+---
+
+## Troubleshooting
+
+| Symptom | Likely cause | Fix |
+|---------|-------------|-----|
+| `ClassNotFoundException: org.postgresql.Driver` | PostgreSQL JDBC driver missing | Add `org.postgresql:postgresql` dependency (see Step 1 guide) |
+| `Cannot connect to database` at startup | DB unreachable but `skipDataSourceCheck` is `false` | Set `.skipDataSourceCheck(true)` |
+| Ebean enhancement warnings in logs | `ebean-maven-plugin` not configured | Complete Step 1 guide |
+| `NullPointerException` reading config key | Config key not defined | Add the key to `application.yml` or environment |
diff --git a/docs/guides/add-ebean-postgres-maven-pom.md b/docs/guides/add-ebean-postgres-maven-pom.md
