Merge branch '2.3.x' into 2.4.x

Closes gh-26159

spring-boot-project/spring-boot-docs/src/main/java/org/springframework/boot/docs/jpa/CustomEntityManagerFactoryExample.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2012-2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.docs.jpa;
+
+import javax.sql.DataSource;
+
+import org.springframework.boot.autoconfigure.orm.jpa.JpaProperties;
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.boot.orm.jpa.EntityManagerFactoryBuilder;
+import org.springframework.context.annotation.Bean;
+import org.springframework.orm.jpa.JpaVendorAdapter;
+import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
+import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
+
+/**
+ * Example configuration for a custom JPA entity manager.
+ *
+ * @author Stephane Nicoll
+ */
+public class CustomEntityManagerFactoryExample {
+
+	// tag::configuration[]
+	@Bean
+	@ConfigurationProperties("app.jpa.first")
+	public JpaProperties firstJpaProperties() {
+		return new JpaProperties();
+	}
+
+	@Bean
+	public LocalContainerEntityManagerFactoryBean firstEntityManagerFactory(DataSource firstDataSource,
+			JpaProperties firstJpaProperties) {
+		EntityManagerFactoryBuilder builder = createEntityManagerFactoryBuilder(firstJpaProperties);
+		return builder.dataSource(firstDataSource).packages(Order.class).persistenceUnit("firstDs").build();
+	}
+
+	private EntityManagerFactoryBuilder createEntityManagerFactoryBuilder(JpaProperties jpaProperties) {
+		JpaVendorAdapter jpaVendorAdapter = createJpaVendorAdapter(jpaProperties);
+		return new EntityManagerFactoryBuilder(jpaVendorAdapter, jpaProperties.getProperties(), null);
+	}
+
+	private JpaVendorAdapter createJpaVendorAdapter(JpaProperties jpaProperties) {
+		// Map JPA properties as needed
+		return new HibernateJpaVendorAdapter();
+	}
+	// end::configuration[]
+
+	private static class Order {
+
+	}
+
+}