JAVA-2305: Move Use Criteria Queries in a Spring Data Application to spring-data-jpa-query-2

persistence-modules/spring-data-jpa-query-2/README.md

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+## Spring Data JPA - Query
+
+This module contains articles about querying data using Spring Data JPA 
+
+### Relevant Articles: 
+- [Use Criteria Queries in a Spring Data Application](https://www.baeldung.com/spring-data-criteria-queries)
+- More articles: [[<-- prev]](../spring-data-jpa-query)
+
+### Eclipse Config 
+After importing the project into Eclipse, you may see the following error:  
+"No persistence xml file found in project"
+
+This can be ignored: 
+- Project -> Properties -> Java Persistance -> JPA -> Error/Warnings -> Select Ignore on "No persistence xml file found in project"
+Or: 
+- Eclipse -> Preferences - Validation - disable the "Build" execution of the JPA Validator 

persistence-modules/spring-data-jpa-query-2/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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>spring-data-jpa-query</artifactId>
+    <name>spring-data-jpa-query-2</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-boot-2</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-boot-2</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-data-jpa</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+        </dependency>
+    </dependencies>
+
+</project>

persistence-modules/spring-data-jpa-query-2/src/main/java/com/baeldung/persistence/dao/BookRepository.java

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+package com.baeldung.persistence.dao;
+
+import com.baeldung.persistence.model.Book;
+import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
+
+public interface BookRepository extends JpaRepository<Book, Long>, BookRepositoryCustom, JpaSpecificationExecutor<Book> {
+
+}

persistence-modules/spring-data-jpa-query-2/src/main/java/com/baeldung/persistence/dao/BookRepositoryCustom.java

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+package com.baeldung.persistence.dao;
+
+import com.baeldung.persistence.model.Book;
+
+import java.util.List;
+
+public interface BookRepositoryCustom {
+
+    List<Book> findBooksByAuthorNameAndTitle(String authorName, String title);
+    
+}

persistence-modules/spring-data-jpa-query-2/src/main/java/com/baeldung/persistence/dao/BookRepositoryImpl.java

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+package com.baeldung.persistence.dao;
+
+import com.baeldung.persistence.model.Book;
+import org.springframework.stereotype.Repository;
+
+import javax.persistence.EntityManager;
+import javax.persistence.TypedQuery;
+import javax.persistence.criteria.CriteriaBuilder;
+import javax.persistence.criteria.CriteriaQuery;
+import javax.persistence.criteria.Predicate;
+import javax.persistence.criteria.Root;
+import java.util.ArrayList;
+import java.util.List;
+
+@Repository
+public class BookRepositoryImpl implements BookRepositoryCustom {
+
+    private EntityManager em;
+
+    public BookRepositoryImpl(EntityManager em) {
+        this.em = em;
+    }
+
+    @Override
+    public List<Book> findBooksByAuthorNameAndTitle(String authorName, String title) {
+        CriteriaBuilder cb = em.getCriteriaBuilder();
+        CriteriaQuery<Book> cq = cb.createQuery(Book.class);
+
+        Root<Book> book = cq.from(Book.class);
+        List<Predicate> predicates = new ArrayList<>();
+
+        if (authorName != null) {
+            predicates.add(cb.equal(book.get("author"), authorName));
+        }
+        if (title != null) {
+            predicates.add(cb.like(book.get("title"), "%" + title + "%"));
+        }
+        cq.where(predicates.toArray(new Predicate[0]));
+
+        TypedQuery<Book> query = em.createQuery(cq);
+        return query.getResultList();
+    }
+
+}

persistence-modules/spring-data-jpa-query-2/src/main/java/com/baeldung/persistence/dao/BookService.java

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+package com.baeldung.persistence.dao;
+
+import com.baeldung.persistence.model.Book;
+import org.springframework.stereotype.Service;
+
+import java.util.List;
+
+import static com.baeldung.persistence.dao.BookSpecifications.hasAuthor;
+import static com.baeldung.persistence.dao.BookSpecifications.titleContains;
+import static org.springframework.data.jpa.domain.Specification.where;
+
+@Service
+public class BookService {
+
+    private BookRepository bookRepository;
+
+    public BookService(BookRepository bookRepository) {
+        this.bookRepository = bookRepository;
+    }
+
+    public List<Book> query(String author, String title) {
+        return bookRepository.findAll(where(hasAuthor(author)).and(titleContains(title)));
+    }
+
+}

persistence-modules/spring-data-jpa-query-2/src/main/java/com/baeldung/persistence/dao/BookSpecifications.java

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+package com.baeldung.persistence.dao;
+
+import com.baeldung.persistence.model.Book;
+import org.springframework.data.jpa.domain.Specification;
+
+public class BookSpecifications {
+
+    public static Specification<Book> hasAuthor(String author) {
+        return (book, cq, cb) -> cb.equal(book.get("author"), author);
+    }
+
+    public static Specification<Book> titleContains(String title) {
+        return (book, cq, cb) -> cb.like(book.get("title"), "%" + title + "%");
+    }
+
+}

persistence-modules/spring-data-jpa-query-2/src/main/java/com/baeldung/persistence/model/Book.java

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+package com.baeldung.persistence.model;
+
+import javax.persistence.Entity;
+import javax.persistence.Id;
+
+@Entity
+public class Book {
+
+    @Id
+    private Long id;
+
+    private String title;
+
+    private String author;
+
+    public Long getId() {
+        return id;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public String getAuthor() {
+        return author;
+    }
+
+    public void setAuthor(String author) {
+        this.author = author;
+    }
+
+}