Spring Boot Querydsl 教程

来源：这里教程网时间：2026-02-17 21:33:08 作者：

Spring Boot Querydsl 教程展示了如何使用 Querydsl 在 Spring Boot 应用中创建数据库查询。

Querydsl

Querydsl 是一个框架，可通过其流畅的 API 来构造静态类型的类似 SQL 的查询。 Spring Data 模块通过QuerydslPredicateExecutor与 Querydsl 集成。

Spring Querydsl 示例

以下应用使用实体管理器和存储库使用 Querydsl 创建查询。

pom.xmlsrc├───main│   ├───java│   │   └───com│   │       └───zetcode│   │           │   Application.java│   │           │   MyRunner.java│   │           ├───model│   │           │       City.java│   │           └───repository│   │                   CityRepository.java│   └───resources│           application.properties│           data-h2.sql│           schema-h2.sql└───test    └───java

这是项目结构。

pom.xml

<?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>    <groupId>com.zetcode</groupId>    <artifactId>springbootquerydsl</artifactId>    <version>1.0-SNAPSHOT</version>    <packaging>jar</packaging>    <properties>        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>        <maven.compiler.source>11</maven.compiler.source>        <maven.compiler.target>11</maven.compiler.target>    </properties>    <parent>        <groupId>org.springframework.boot</groupId>        <artifactId>spring-boot-starter-parent</artifactId>        <version>2.1.5.RELEASE</version>    </parent>    <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>com.querydsl</groupId>            <artifactId>querydsl-apt</artifactId>            <version>4.2.1</version>            <scope>provided</scope>        </dependency>        <dependency>            <groupId>com.querydsl</groupId>            <artifactId>querydsl-jpa</artifactId>            <version>4.2.1</version>        </dependency>    </dependencies>    <build>        <plugins>            <plugin>                <groupId>org.springframework.boot</groupId>                <artifactId>spring-boot-maven-plugin</artifactId>            </plugin>            <!--Plugin for query-dsl-->            <plugin>                <groupId>com.mysema.maven</groupId>                <artifactId>apt-maven-plugin</artifactId>                <version>1.1.3</version>                <executions>                    <execution>                        <phase>generate-sources</phase>                        <goals>                            <goal>process</goal>                        </goals>                        <configuration>                            <outputDirectory>target/generated-sources/java</outputDirectory>                            <processor>com.querydsl.apt.jpa.JPAAnnotationProcessor</processor>                        </configuration>                    </execution>                </executions>            </plugin>        </plugins>    </build></project>

Maven POM 文件包含 Spring Data JPA，H2 数据库和 Querydsl 的依赖项。 JPAAnnotationProcessor查找带有Entity注解的域类型，并为其生成查询类型。

注解处理是 javac 中的一种工具，用于在编译时扫描和处理注解。

resources/application.properties

spring.main.banner-mode=offspring.datasource.platform=h2spring.jpa.hibernate.ddl-auto=nonelogging.pattern.console=%d{dd-MM-yyyy HH:mm:ss} %magenta([%thread]) %highlight(%-5level) %logger.%M - %msg%n

application.properties是主要的 Spring Boot 配置文件。使用spring.main.banner-mode属性，我们可以关闭 Spring 标语。 spring.datasource.platform设置数据库的供应商名称。在初始化脚本中使用它。最后，spring.jpa.hibernate.ddl-auto禁止从实体自动创建模式。 logging.pattern.console定义控制台的日志模式。

resources/schema-h2.sql

CREATE TABLE cities(id INT PRIMARY KEY AUTO_INCREMENT,    name VARCHAR(255), population INT);

启动应用时，将执行schema-h2.sql脚本。它创建一个新的数据库表。

resources/data-h2.sql

INSERT INTO cities(name, population) VALUES('Bratislava', 432000);INSERT INTO cities(name, population) VALUES('Budapest', 1759000);INSERT INTO cities(name, population) VALUES('Prague', 1280000);INSERT INTO cities(name, population) VALUES('Warsaw', 1748000);INSERT INTO cities(name, population) VALUES('Los Angeles', 3971000);INSERT INTO cities(name, population) VALUES('New York', 8550000);INSERT INTO cities(name, population) VALUES('Edinburgh', 464000);INSERT INTO cities(name, population) VALUES('Suzhou', 4327066);INSERT INTO cities(name, population) VALUES('Zhengzhou', 4122087);INSERT INTO cities(name, population) VALUES('Berlin', 3671000);INSERT INTO cities(name, population) VALUES('Brest', 139163);INSERT INTO cities(name, population) VALUES('Bucharest', 1836000);

之后，执行data-h2.sql文件。它用数据填充表。

com/zetcode/model/City.java

package com.zetcode.model;import java.util.Objects;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.Table;@Entity@Table(name = "cities")public class City {    @Id    @GeneratedValue(strategy = GenerationType.AUTO)    private Long id;    private String name;    private int population;    public City() {    }    public City(String name, int population) {        this.name = name;        this.population = population;    }    public Long getId() {        return id;    }    public void setId(Long id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public int getPopulation() {        return population;    }    public void setPopulation(int population) {        this.population = population;    }    @Override    public int hashCode() {        int hash = 7;        hash = 79 * hash + Objects.hashCode(this.id);        hash = 79 * hash + Objects.hashCode(this.name);        hash = 79 * hash + this.population;        return hash;    }    @Override    public boolean equals(Object obj) {        if (this == obj) {            return true;        }        if (obj == null) {            return false;        }        if (getClass() != obj.getClass()) {            return false;        }        final City other = (City) obj;        if (this.population != other.population) {            return false;        }        if (!Objects.equals(this.name, other.name)) {            return false;        }        return Objects.equals(this.id, other.id);    }    @Override    public String toString() {        var builder = new StringBuilder();        builder.append("City{id=").append(id).append(", name=")                .append(name).append(", population=")                .append(population).append("}");        return builder.toString();    }}

这是City实体。

com/zetcode/repository/CityRepository.java

package com.zetcode.repository;import com.zetcode.model.City;import org.springframework.data.querydsl.QuerydslPredicateExecutor;import org.springframework.data.repository.CrudRepository;import org.springframework.stereotype.Repository;@Repositorypublic interface CityRepository extends CrudRepository<City, Long>,        QuerydslPredicateExecutor<City> {}

要在我们的存储库中启用 Querydsl，我们从QuerydslPredicateExecutor扩展。

com/zetcode/MyRunner.java

package com.zetcode;import com.querydsl.core.types.OrderSpecifier;import com.querydsl.core.types.dsl.BooleanExpression;import com.querydsl.jpa.impl.JPAQuery;import com.zetcode.model.QCity;import com.zetcode.repository.CityRepository;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.CommandLineRunner;import org.springframework.stereotype.Component;import javax.persistence.EntityManager;import javax.persistence.PersistenceContext;@Component@SuppressWarnings({ "rawtypes", "unchecked" })public class MyRunner implements CommandLineRunner {    private static final Logger logger = LoggerFactory.getLogger(MyRunner.class);    @PersistenceContext    private EntityManager entityManager;    @Autowired    private CityRepository cityRepository;    @Override    public void run(String... args) throws Exception {        var qCity = QCity.city;        var query = new JPAQuery(entityManager);        query.from(qCity).where(qCity.name.eq("Bratislava")).distinct();        var c1 = query.fetch();        logger.info("{}", c1);        var query2 = new JPAQuery(entityManager);        query2.from(qCity).where(qCity.name.endsWith("est").and(qCity.population.lt(1800000)));        var cities = query2.fetch();        logger.info("{}", cities);        BooleanExpression booleanExpression = qCity.population.goe(2_000_000);        OrderSpecifier<String> orderSpecifier = qCity.name.asc();        var cities2 = cityRepository.findAll(booleanExpression, orderSpecifier);        logger.info("{}", cities2);    }}

我们使用EntityManager和CityRepository创建 Querydsl 查询。

var qCity = QCity.city;

Querydsl 创建一个QCity类型。

var query = new JPAQuery(entityManager);

在前两个查询中，我们使用实体管理器。

query.from(qCity).where(qCity.name.eq("Bratislava")).distinct();var c1 = query.fetch();logger.info("{}", c1);

使用 Querydsl 的流畅 API，我们获取了一个独特的城市对象。

var query2 = new JPAQuery(entityManager);query2.from(qCity).where(qCity.name.endsWith("est").and(qCity.population.lt(1800000)));var cities = query2.fetch();logger.info("{}", cities);

一个更复杂的查询将获取多个城市。

BooleanExpression booleanExpression = qCity.population.goe(2_000_000);OrderSpecifier<String> orderSpecifier = qCity.name.asc();var cities2 = cityRepository.findAll(booleanExpression, orderSpecifier);logger.info("{}", cities2);

在第三个查询中，我们利用存储库。

Note: In Java enterprise applications it is a good practice to define a service layer that works with repositories. For simplicity reasons, we skip the service layer.

com/zetcode/Application.java

package com.zetcode;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplicationpublic class Application {    public static void main(String[] args) {        SpringApplication.run(Application.class, args);    }}

Application设置 Spring Boot 应用。 @SpringBootApplication启用自动配置和组件扫描。

$ mvn spring-boot:run...04-06-2019 13:22:13 [main] INFO  com.zetcode.MyRunner.run - [City{id=1, name=Bratislava, population=432000}]04-06-2019 13:22:13 [main] INFO  com.zetcode.MyRunner.run - [City{id=2, name=Budapest, population=1759000}, City{id=11, name=Brest, population=139163}]04-06-2019 13:22:13 [main] INFO  com.zetcode.MyRunner.run - [City{id=10, name=Berlin, population=3671000}, City{id=5, name=Los Angeles, population=3971000}, City{id=6, name=New York, population=8550000}, City{id=8, name=Suzhou, population=4327066}, City{id=9, name=Zhengzhou, population=4122087}]...

我们运行该应用。

在本教程中，我们展示了如何使用 Querydsl 在 Spring Boot 应用中生成查询。