Add MongoDB example for linking documents.

Closes #631

mongodb/linking/src/main/java/example/springdata/mongodb/linking/dbref/ApplicationConfiguration.java

@@ -0,0 +1,24 @@
+/*
+ * Copyright 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 example.springdata.mongodb.linking.dbref;
+
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+/**
+ * @author Christoph Strobl
+ */
+@SpringBootApplication
+class ApplicationConfiguration {}

mongodb/linking/src/main/java/example/springdata/mongodb/linking/dbref/Employee.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright 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 example.springdata.mongodb.linking.dbref;
+
+import org.springframework.data.annotation.Id;
+import org.springframework.data.mongodb.core.mapping.DBRef;
+
+/**
+ * @author Christoph Strobl
+ */
+class Employee {
+
+	@Id
+	private String id;
+	private String name;
+
+	@DBRef(lazy = true) // lazy to avoid stackoverflow on load
+	private Manager manager;
+
+	public Employee() {
+	}
+
+	public Employee(String id, String name) {
+		this.id = id;
+		this.name = name;
+	}
+
+	public String getId() {
+		return id;
+	}
+
+	public void setId(String id) {
+		this.id = id;
+	}
+
+	public String getName() {
+		return name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+	public Manager getManager() {
+		return manager;
+	}
+
+	public void setManager(Manager manager) {
+		this.manager = manager;
+	}
+}

mongodb/linking/src/main/java/example/springdata/mongodb/linking/dbref/Manager.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright 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 example.springdata.mongodb.linking.dbref;
+
+import java.util.List;
+
+import org.springframework.data.annotation.Id;
+import org.springframework.data.mongodb.core.mapping.DBRef;
+
+/**
+ * @author Christoph Strobl
+ */
+class Manager {
+
+	@Id //
+	private String id;
+	private String name;
+
+	@DBRef //
+	private List<Employee> employees;
+
+	public Manager() {
+	}
+
+	public Manager(String id, String name) {
+		this.id = id;
+		this.name = name;
+	}
+
+	public String getId() {
+		return id;
+	}
+
+	public void setId(String id) {
+		this.id = id;
+	}
+
+	public String getName() {
+		return name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+	public List<Employee> getEmployees() {
+		return employees;
+	}
+
+	public void setEmployees(List<Employee> employees) {
+		this.employees = employees;
+	}
+}

mongodb/linking/src/main/java/example/springdata/mongodb/linking/docref/jpastyle/ApplicationConfiguration.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright 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 example.springdata.mongodb.linking.docref.jpastyle;
+
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+/**
+ * @author Christoph Strobl
+ */
+@SpringBootApplication
+class ApplicationConfiguration {
+
+}

mongodb/linking/src/main/java/example/springdata/mongodb/linking/docref/jpastyle/Employee.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 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 example.springdata.mongodb.linking.docref.jpastyle;
+
+import org.springframework.data.annotation.Id;
+
+/**
+ * @author Christoph Strobl
+ */
+class Employee {
+
+	@Id
+	private String id;
+	private String name;
+
+	/**
+	 * Only hold the id of the manager to link to it.
+	 */
+	private String managerId;
+
+	public Employee() {
+	}
+
+	public Employee(String id, String name) {
+		this.id = id;
+		this.name = name;
+	}
+
+	public String getId() {
+		return id;
+	}
+
+	public void setId(String id) {
+		this.id = id;
+	}
+
+	public String getName() {
+		return name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+	public String getManagerId() {
+		return managerId;
+	}
+
+	public void setManagerId(String managerId) {
+		this.managerId = managerId;
+	}
+}

mongodb/linking/src/main/java/example/springdata/mongodb/linking/docref/jpastyle/Manager.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright 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 example.springdata.mongodb.linking.docref.jpastyle;
+
+import java.util.List;
+
+import org.springframework.data.annotation.Id;
+import org.springframework.data.annotation.ReadOnlyProperty;
+import org.springframework.data.mongodb.core.mapping.DocumentReference;
+
+/**
+ * @author Christoph Strobl
+ */
+class Manager {
+
+	@Id //
+	private String id;
+	private String name;
+
+	/**
+	 * Uses the {@literal this.id} to look up documents in the {@literal employee} collection
+	 * that have a matching {@literal managerId} field value.
+	 */
+	@ReadOnlyProperty
+	@DocumentReference(lookup="{'managerId':?#{#self._id} }")
+	private List<Employee> employees;
+
+	public Manager() {
+	}
+
+	public Manager(String id, String name) {
+		this.id = id;
+		this.name = name;
+	}
+
+	public String getId() {
+		return id;
+	}
+
+	public void setId(String id) {
+		this.id = id;
+	}
+
+	public String getName() {
+		return name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+	public List<Employee> getEmployees() {
+		return employees;
+	}
+
+	public void setEmployees(List<Employee> employees) {
+		this.employees = employees;
+	}
+}

mongodb/linking/src/main/java/example/springdata/mongodb/linking/docref/query/ApplicationConfiguration.java

@@ -0,0 +1,24 @@
+/*
+ * Copyright 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 example.springdata.mongodb.linking.docref.query;
+
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+/**
+ * @author Christoph Strobl
+ */
+@SpringBootApplication
+class ApplicationConfiguration {}

mongodb/linking/src/main/java/example/springdata/mongodb/linking/docref/query/Employee.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright 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 example.springdata.mongodb.linking.docref.query;
+
+import org.springframework.data.annotation.Id;
+import org.springframework.data.mongodb.core.mapping.DocumentReference;
+
+/**
+ * @author Christoph Strobl
+ */
+class Employee {
+
+	@Id
+	private String id;
+	private String name;
+
+	@DocumentReference(lazy = true) // lazy to avoid stackoverflow on load
+	private Manager manager;
+
+	public Employee() {
+	}
+
+	public Employee(String id, String name) {
+		this.id = id;
+		this.name = name;
+	}
+
+	public String getId() {
+		return id;
+	}
+
+	public void setId(String id) {
+		this.id = id;
+	}
+
+	public String getName() {
+		return name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+	public Manager getManager() {
+		return manager;
+	}
+
+	public void setManager(Manager manager) {
+		this.manager = manager;
+	}
+}

mongodb/linking/src/main/java/example/springdata/mongodb/linking/docref/query/Manager.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright 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 example.springdata.mongodb.linking.docref.query;
+
+import java.util.List;
+
+import org.springframework.data.annotation.Id;
+import org.springframework.data.mongodb.core.mapping.DocumentReference;
+
+/**
+ * @author Christoph Strobl
+ */
+class Manager {
+
+	@Id //
+	private String id;
+	private String name;
+
+	/**
+	 * Uses the value stored in the {@literal employees} field of the {@literal manager} document to look up
+	 * documents in the {@literal employee} collection that have a matching {@literal name} field value.
+	 */
+	@DocumentReference(lookup = "{ 'name' : ?#{#target} }") //
+	private List<Employee> employees;
+
+	public Manager() {
+	}
+
+	public Manager(String id, String name) {
+		this.id = id;
+		this.name = name;
+	}
+
+	public String getId() {
+		return id;
+	}
+
+	public void setId(String id) {
+		this.id = id;
+	}
+
+	public String getName() {
+		return name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+	public List<Employee> getEmployees() {
+		return employees;
+	}
+
+	public void setEmployees(List<Employee> employees) {
+		this.employees = employees;
+	}
+}

mongodb/linking/src/main/java/example/springdata/mongodb/linking/docref/simple/ApplicationConfiguration.java

@@ -0,0 +1,24 @@
+/*
+ * Copyright 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 example.springdata.mongodb.linking.docref.simple;
+
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+/**
+ * @author Christoph Strobl
+ */
+@SpringBootApplication
+class ApplicationConfiguration {}

mongodb/linking/src/main/java/example/springdata/mongodb/linking/docref/simple/Employee.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 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 example.springdata.mongodb.linking.docref.simple;
+
+import org.springframework.data.annotation.Id;
+import org.springframework.data.mongodb.core.mapping.DBRef;
+import org.springframework.data.mongodb.core.mapping.DocumentReference;
+
+/**
+ * @author Christoph Strobl
+ */
+class Employee {
+
+	@Id
+	private String id;
+	private String name;
+
+	@DocumentReference(lazy = true) // lazy to avoid stackoverflow on load
+	private Manager manager;
+
+	public Employee() {
+	}
+
+	public Employee(String id, String name) {
+		this.id = id;
+		this.name = name;
+	}
+
+	public String getId() {
+		return id;
+	}
+
+	public void setId(String id) {
+		this.id = id;
+	}
+
+	public String getName() {
+		return name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+	public Manager getManager() {
+		return manager;
+	}
+
+	public void setManager(Manager manager) {
+		this.manager = manager;
+	}
+}

mongodb/linking/src/main/java/example/springdata/mongodb/linking/docref/simple/Manager.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright 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 example.springdata.mongodb.linking.docref.simple;
+
+import java.util.List;
+
+import org.springframework.data.annotation.Id;
+import org.springframework.data.mongodb.core.mapping.DocumentReference;
+
+/**
+ * @author Christoph Strobl
+ */
+class Manager {
+
+	@Id //
+	private String id;
+	private String name;
+
+	/**
+	 * Uses the value stored in the {@literal employees} field of the {@literal manager} document to look up
+	 * documents in the {@literal employee} collection that have a matching {@literal _id} field value.
+	 */
+	@DocumentReference //
+	private List<Employee> employees;
+
+	public Manager() {
+	}
+
+	public Manager(String id, String name) {
+		this.id = id;
+		this.name = name;
+	}
+
+	public String getId() {
+		return id;
+	}
+
+	public void setId(String id) {
+		this.id = id;
+	}
+
+	public String getName() {
+		return name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+	public List<Employee> getEmployees() {
+		return employees;
+	}
+
+	public void setEmployees(List<Employee> employees) {
+		this.employees = employees;
+	}
+}

mongodb/linking/src/test/java/example/springdata/mongodb/linking/dbref/DBRefTests.java

@@ -0,0 +1,81 @@
+/*
+ * Copyright 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 example.springdata.mongodb.linking.dbref;
+
+import static org.assertj.core.api.Assertions.*;
+import static org.springframework.data.mongodb.core.query.Criteria.*;
+
+import java.util.List;
+
+import com.mongodb.DBRef;
+import org.bson.Document;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.data.mongo.DataMongoTest;
+import org.springframework.data.mongodb.core.MongoOperations;
+import org.springframework.data.mongodb.core.query.Update;
+
+/**
+ * @author Christoph Strobl
+ */
+@DataMongoTest
+public class DBRefTests {
+
+	@Autowired MongoOperations operations;
+
+	@Test
+	void saveAndLoadDbRef() {
+
+		Manager manager = new Manager("jabba-the-hutt", "jabba");
+
+		operations.save(manager);
+
+		Employee employee1 = new Employee("greedo-tetsu-jr", "greedo");
+		employee1.setManager(manager);
+		operations.save(employee1);
+		operations.update(Manager.class) //
+				.matching(where("id").is(manager.getId())) //
+				.apply(new Update().push("employees").value(employee1)) //
+				.first();
+
+		Employee employee2 = new Employee("boba-fett", "boba");
+		employee2.setManager(manager);
+		operations.save(employee2);
+		operations.update(Manager.class) //
+				.matching(where("id").is(manager.getId())) //
+				.apply(new Update().push("employees").value(employee2)) //
+				.first();
+
+		operations.execute(Manager.class, collection -> {
+
+			Document rawManager = collection.find(new Document("_id", manager.getId())).first();
+			assertThat(rawManager.get("employees", List.class)) //
+					.containsExactly( //
+							new DBRef("employee", "greedo-tetsu-jr"), //
+							new DBRef("employee", "boba-fett") //
+					);
+			return "OK";
+		});
+
+		Manager loaded = operations.query(Manager.class)
+				.matching(where("id").is(manager.getId()))
+				.firstValue();
+
+		assertThat(loaded.getEmployees()) //
+				.allMatch(it -> it instanceof Employee) //
+				.extracting("name").containsExactly("greedo", "boba");
+	}
+}

mongodb/linking/src/test/java/example/springdata/mongodb/linking/docref/jpastyle/JpaStyleDocRefTests.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright 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 example.springdata.mongodb.linking.docref.jpastyle;
+
+import static org.assertj.core.api.Assertions.*;
+import static org.springframework.data.mongodb.core.query.Criteria.*;
+
+import org.bson.Document;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.data.mongo.DataMongoTest;
+import org.springframework.data.mongodb.core.MongoOperations;
+
+/**
+ * @author Christoph Strobl
+ */
+@DataMongoTest
+public class JpaStyleDocRefTests {
+
+	@Autowired MongoOperations operations;
+
+	/**
+	 * Load linked documents where where the actual reference is stored in the obverse side of the association.
+	 */
+	@Test
+	void saveAndLoadJpaStyleRelation() {
+
+		Manager manager = new Manager("jabba-the-hutt", "jabba");
+
+		operations.save(manager);
+
+		Employee employee1 = new Employee("greedo-tetsu-jr", "greedo");
+		employee1.setManagerId(manager.getId()); // establish the link to the manager document
+		operations.save(employee1);
+		// no need to update he manager document after save of employee
+
+		Employee employee2 = new Employee("boba-fett", "boba");
+		employee2.setManagerId(manager.getId()); // establish the link to the manager document
+		operations.save(employee2);
+		// no need to update he manager document after save of employee
+
+		operations.execute(Manager.class, collection -> {
+
+			Document rawManager = collection.find(new Document("_id", manager.getId())).first();
+			assertThat(rawManager).doesNotContainKey("employees");
+			return "OK";
+		});
+
+		Manager loaded = operations.query(Manager.class)
+				.matching(where("id").is(manager.getId()))
+				.firstValue();
+
+		assertThat(loaded.getEmployees()) //
+				.allMatch(it -> it instanceof Employee) //
+				.extracting("name").containsExactly("greedo", "boba");
+	}
+}

mongodb/linking/src/test/java/example/springdata/mongodb/linking/docref/query/QueryDocRefTests.java

@@ -0,0 +1,81 @@
+/*
+ * Copyright 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 example.springdata.mongodb.linking.docref.query;
+
+import static org.assertj.core.api.Assertions.*;
+import static org.springframework.data.mongodb.core.query.Criteria.*;
+
+import java.util.List;
+
+import org.bson.Document;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.data.mongo.DataMongoTest;
+import org.springframework.data.mongodb.core.MongoOperations;
+import org.springframework.data.mongodb.core.query.Update;
+
+/**
+ * @author Christoph Strobl
+ */
+@DataMongoTest
+public class QueryDocRefTests {
+
+	@Autowired MongoOperations operations;
+
+	/**
+	 * Load linked documents where where the reference is stored on the inverse and evaluated against a non id property on
+	 * the obverse side of the association.
+	 */
+	@Test
+	void saveAndLoadDocRefViaQuery() {
+
+		Manager manager = new Manager("jabba-the-hutt", "jabba");
+
+		operations.save(manager);
+
+		Employee employee1 = new Employee("greedo-tetsu-jr", "greedo");
+		employee1.setManager(manager); // back-link to the manager document
+		operations.save(employee1);
+		operations.update(Manager.class) // establish the link to the employee document via employee.name
+				.matching(where("id").is(manager.getId())) //
+				.apply(new Update().push("employees").value(employee1.getName())) //
+				.first();
+
+		Employee employee2 = new Employee("boba-fett", "boba");
+		employee2.setManager(manager); //  back-link to the manager document
+		operations.save(employee2);
+		operations.update(Manager.class) // establish the link to the employee document via employee.name
+				.matching(where("id").is(manager.getId())) //
+				.apply(new Update().push("employees").value(employee2.getName())) //
+				.first();
+
+		operations.execute(Manager.class, collection -> {
+
+			Document rawManager = collection.find(new Document("_id", manager.getId())).first();
+			assertThat(rawManager.get("employees", List.class)) //
+					.containsExactly("greedo", "boba");
+			return "OK";
+		});
+
+		Manager loaded = operations.query(Manager.class)
+				.matching(where("id").is(manager.getId()))
+				.firstValue();
+
+		assertThat(loaded.getEmployees()) //
+				.allMatch(it -> it instanceof Employee) //
+				.extracting("name").containsExactly("greedo", "boba");
+	}
+}

mongodb/linking/src/test/java/example/springdata/mongodb/linking/docref/simple/SimpleDocRefTests.java

@@ -0,0 +1,81 @@
+/*
+ * Copyright 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 example.springdata.mongodb.linking.docref.simple;
+
+import static org.assertj.core.api.Assertions.*;
+import static org.springframework.data.mongodb.core.query.Criteria.*;
+
+import java.util.List;
+
+import org.bson.Document;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.data.mongo.DataMongoTest;
+import org.springframework.data.mongodb.core.MongoOperations;
+import org.springframework.data.mongodb.core.query.Update;
+
+/**
+ * @author Christoph Strobl
+ */
+@DataMongoTest
+public class SimpleDocRefTests {
+
+	@Autowired MongoOperations operations;
+
+	/**
+	 * Load linked documents where where the reference is stored on the inverse and evaluated against the id property on
+	 * the obverse side of the association.
+	 */
+	@Test
+	void saveAndLoadDocRef() {
+
+		Manager manager = new Manager("jabba-the-hutt", "jabba");
+
+		operations.save(manager);
+
+		Employee employee1 = new Employee("greedo-tetsu-jr", "greedo");
+		employee1.setManager(manager); // back-link to the manager document
+		operations.save(employee1);
+		operations.update(Manager.class) // establish the link to the employee document via employee.id
+				.matching(where("id").is(manager.getId())) //
+				.apply(new Update().push("employees").value(employee1)) //
+				.first();
+
+		Employee employee2 = new Employee("boba-fett", "boba");
+		employee2.setManager(manager); // back-link to the manager document
+		operations.save(employee2);
+		operations.update(Manager.class) // establish the link to the employee document via employee.id
+				.matching(where("id").is(manager.getId())) //
+				.apply(new Update().push("employees").value(employee2)) //
+				.first();
+
+		operations.execute(Manager.class, collection -> {
+
+			Document rawManager = collection.find(new Document("_id", manager.getId())).first();
+			assertThat(rawManager.get("employees", List.class)) //
+					.containsExactly("greedo-tetsu-jr", "boba-fett");
+			return "OK";
+		});
+
+		Manager loaded = operations.query(Manager.class)
+				.matching(where("id").is(manager.getId()))
+				.firstValue();
+
+		assertThat(loaded.getEmployees()) //
+				.allMatch(it -> it instanceof Employee) //
+				.extracting("name").containsExactly("greedo", "boba");
+	}
+}

mongodb/linking/src/test/resources/application.properties

@@ -0,0 +1,3 @@
+# Random port for embedded MongoDB
+spring.data.mongodb.port=0
+spring.mongodb.embedded.version=3.6.0