spring data projections

spring-data-projection/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<parent>
+		<groupId>org.springframework.boot</groupId>
+		<artifactId>spring-boot-starter-parent</artifactId>
+		<version>2.4.3</version>
+		<relativePath/> <!-- lookup parent from repository -->
+	</parent>
+	<groupId>ru.sysout</groupId>
+	<artifactId>spring-data-projections</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+	<name>spring-data-projections</name>
+	<description>Demo project for Spring Boot</description>
+	<properties>
+		<java.version>11</java.version>
+	</properties>
+	<dependencies>
+
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-data-jpa</artifactId>
+		</dependency>
+
+
+		<dependency>
+			<groupId>com.h2database</groupId>
+			<artifactId>h2</artifactId>
+			<scope>runtime</scope>
+		</dependency>
+
+		<dependency>
+			<groupId>org.projectlombok</groupId>
+			<artifactId>lombok</artifactId>
+			<optional>true</optional>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+	</dependencies>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.springframework.boot</groupId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
+				<configuration>
+					<excludes>
+						<exclude>
+							<groupId>org.projectlombok</groupId>
+							<artifactId>lombok</artifactId>
+						</exclude>
+					</excludes>
+				</configuration>
+			</plugin>
+		</plugins>
+	</build>
+
+</project>

spring-data-projection/src/main/java/ru/sysout/projections/Main.java

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+package ru.sysout.projections;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class Main {
+
+
+	public static void main(String[] args) {
+		SpringApplication.run(Main.class, args);
+	}
+
+}

spring-data-projection/src/main/java/ru/sysout/projections/dao/PostRepository.java

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+package ru.sysout.projections.dao;
+
+
+import org.springframework.data.jpa.repository.JpaRepository;
+import ru.sysout.projections.dto.PostView;
+import ru.sysout.projections.model.Post;
+
+import java.util.List;
+
+public interface PostRepository extends JpaRepository<Post, Long> {
+
+    List<PostView> findByTitle(String title);
+}

spring-data-projection/src/main/java/ru/sysout/projections/dao/UserRepository.java

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+package ru.sysout.projections.dao;
+
+
+import org.springframework.data.jpa.repository.JpaRepository;
+import ru.sysout.projections.dto.UserDto;
+import ru.sysout.projections.dto.UserView;
+import ru.sysout.projections.model.User;
+
+import java.util.List;
+
+public interface UserRepository extends JpaRepository<User, Long> {
+
+    UserView findByNickname(String nickname);
+
+    List<UserDto> findByEmail(String email);
+
+    <T> T findByNickname(String nickname, Class<T> type);
+}

spring-data-projection/src/main/java/ru/sysout/projections/dto/PostView.java

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+package ru.sysout.projections.dto;
+
+public interface PostView {
+
+    long getId();
+    String getTitle();
+    UserView getUser();
+}

spring-data-projection/src/main/java/ru/sysout/projections/dto/UserDto.java

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+package ru.sysout.projections.dto;
+
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+
+@Getter
+@AllArgsConstructor
+public class UserDto {
+    private Long id;
+    private String nickname;
+
+}

spring-data-projection/src/main/java/ru/sysout/projections/dto/UserView.java

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+package ru.sysout.projections.dto;
+
+
+import org.springframework.beans.factory.annotation.Value;
+
+public interface UserView {
+
+    String getNickname();
+
+    @Value("#{target.email + ' ' + target.password}")
+    String getInfo();
+}

spring-data-projection/src/main/java/ru/sysout/projections/model/Post.java

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+package ru.sysout.projections.model;
+
+import lombok.Data;
+import lombok.NoArgsConstructor;
+import org.hibernate.annotations.CreationTimestamp;
+
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.Id;
+import javax.persistence.ManyToOne;
+import java.time.LocalDateTime;
+
+@Entity
+@Data
+@NoArgsConstructor
+public class Post {
+    @Id
+    @GeneratedValue(generator = "sequence")
+    private Long id;
+
+    private String title;
+
+    private String text;
+
+    @CreationTimestamp
+    private LocalDateTime createdDateTime;
+
+    @ManyToOne
+    private User user;
+}

spring-data-projection/src/main/java/ru/sysout/projections/model/User.java

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+package ru.sysout.projections.model;
+
+
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.Id;
+
+@Data
+@Entity
+@NoArgsConstructor
+public class User {
+    @Id
+    @GeneratedValue(generator = "sequence")
+    private Long id;
+
+    private String email;
+
+    private String nickname;
+
+
+    private String password;
+
+    private String role="ROLE_USER";
+
+    private boolean locked=false;
+
+}

spring-data-projection/src/main/resources/application.properties

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+spring.h2.console.enabled=true
+spring.datasource.url=jdbc:h2:mem:testdb
+spring.jpa.hibernate.ddl-auto=none
+spring.jpa.show-sql=true

spring-data-projection/src/main/resources/data.sql

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+insert into user (id, email, nickname, password, role, locked) values (1,'admin@example.com', 'admin', 'password', 'ROLE_ADMIN', false);
+insert into user (id, email, nickname, password, role, locked) values (2,'user@example.com', 'bob', 'password', 'ROLE_USER', false);
+
+insert into post (id, title, text, created_date_time, user_id) values (3,'Super Post3', 'Super Text3', CURRENT_TIMESTAMP(), 1);
+insert into post (id, title, text, created_date_time, user_id) values (4,'Super Post4', 'Super Text4', CURRENT_TIMESTAMP(), 1);
+insert into post (id, title, text, created_date_time, user_id) values (5,'Super Post5', 'Super Text5', CURRENT_TIMESTAMP(), 1);
+
+

spring-data-projection/src/main/resources/schema.sql

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+CREATE TABLE IF NOT EXISTS USER (
+     id integer not null,
+     email varchar(255) not null,
+     nickname varchar(255) not null,
+     password varchar(255) not null,
+     role varchar(255) not null,
+     locked boolean,
+     primary key (id)
+);
+ALTER TABLE
+    USER
+    ADD CONSTRAINT EMAIL_UNIQUE
+        UNIQUE (email);
+ALTER TABLE
+    USER
+    ADD CONSTRAINT NICKNAME_UNIQUE
+        UNIQUE (nickname);
+
+
+CREATE TABLE IF NOT EXISTS POST (
+     id integer not null,
+     title varchar(255),
+     text clob,
+     created_date_time timestamp,
+     user_id integer not null,
+     primary key (id)
+);
+ALTER TABLE POST
+ADD FOREIGN KEY (user_id) REFERENCES USER(id);
+
+create sequence hiber_sequence MINVALUE 10;

spring-data-projection/src/test/java/ru/sysout/projections/dao/PostRepositoryTest.java

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+package ru.sysout.projections.dao;
+
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import ru.sysout.projections.dto.PostView;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+import static org.junit.jupiter.api.Assertions.assertLinesMatch;
+
+@SpringBootTest
+public class PostRepositoryTest {
+    @Autowired
+    private PostRepository postRepository;
+
+    @Test
+    public void shouldFindInterfaceProjection() {
+        List<PostView> list = postRepository.findByTitle("Super Post3");
+
+        List expected = List.of("Super Post3");
+
+        List actual = list.stream().map(el -> el.getTitle()).collect(Collectors.toList());
+
+        assertLinesMatch(expected, actual);
+
+    }
+
+
+
+}

spring-data-projection/src/test/java/ru/sysout/projections/dao/UserRepositoryTest.java

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+package ru.sysout.projections.dao;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import ru.sysout.projections.dto.UserDto;
+import ru.sysout.projections.dto.UserView;
+import ru.sysout.projections.model.User;
+
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+@SpringBootTest
+public class UserRepositoryTest {
+    @Autowired
+    private UserRepository userRepository;
+
+    @Test
+    public void shouldFindOpenProjection() {
+        UserView userView = userRepository.findByNickname("admin");
+
+        assertEquals("admin@example.com password", userView.getInfo());
+    }
+
+    @Test
+    public void shouldFindClassProjection() {
+        List<UserDto> userDtos = userRepository.findByEmail("admin@example.com");
+        UserDto userDto = userDtos.get(0);
+        assertEquals("admin", userDto.getNickname());
+    }
+
+    @Test
+    public void shouldFindDynamicProjection() {
+        UserDto userDto = userRepository.findByNickname("admin", UserDto.class);
+        assertEquals("admin", userDto.getNickname());
+
+        User user = userRepository.findByNickname("admin", User.class);
+        assertEquals("admin", user.getNickname());
+
+        UserView userView = userRepository.findByNickname("admin", UserView.class);
+        assertEquals("admin", userView.getNickname());
+    }
+}