1.导入依赖

<?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.jmj</groupId><artifactId>springDataJPA-Springboot</artifactId><version>1.0-SNAPSHOT</version><properties><maven.compiler.source>8</maven.compiler.source><maven.compiler.target>8</maven.compiler.target><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><querydsl.version>4.4.0</querydsl.version><apt.version>1.1.3</apt.version><!--    声明springboot的版本号 --><spring-boot.version>2.5.5</spring-boot.version></properties><!--  引入springboot官方提供的所有依赖的版本号定义，如果项目中使用相关依赖，可以不必写版本号了--><dependencyManagement><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-dependencies</artifactId><version>${spring-boot.version}</version><type>pom</type><scope>import</scope></dependency></dependencies></dependencyManagement><dependencies><!--    引入springboot的web项目的依赖        --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><!--     data - jpa 启动器  --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-jpa</artifactId></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.47</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId></dependency><!--        druid连接--><dependency><groupId>com.alibaba</groupId><artifactId>druid-spring-boot-starter</artifactId><version>1.2.6</version></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId></dependency><dependency><groupId>com.querydsl</groupId><artifactId>querydsl-jpa</artifactId><version>${querydsl.version}</version></dependency></dependencies><!--  这个插件是为了让程序自动生成query type （查询实体，命名方式为:"Q"+对应实体名） maven插件 --><build><plugins><plugin><groupId>com.mysema.maven</groupId><artifactId>apt-maven-plugin</artifactId><version>${apt.version}</version><dependencies><dependency><groupId>com.querydsl</groupId><artifactId>querydsl-apt</artifactId><version>${querydsl.version}</version></dependency></dependencies><executions><execution><phase>generate-sources</phase><goals><goal>process</goal></goals><configuration><outputDirectory>target/generated-sources/queries</outputDirectory><processor>com.querydsl.apt.jpa.JPAAnnotationProcessor</processor><logOnlyOnError>true</logOnlyOnError></configuration></execution></executions></plugin></plugins></build></project>

2.mapper

package com.jmj.springDataApp.mapper;import com.jmj.springDataApp.pojo.Student;
import org.springframework.data.querydsl.QuerydslPredicateExecutor;
import org.springframework.data.repository.PagingAndSortingRepository;public interface StudentDSLMapper extends PagingAndSortingRepository<Student,Long> , QuerydslPredicateExecutor<Student> {
}

3.test

package com.jmj.springDataApp.mapper;import com.jmj.springDataApp.pojo.QStudent;
import com.jmj.springDataApp.pojo.Student;
import com.querydsl.core.types.Predicate;
import com.querydsl.core.types.Visitor;
import com.querydsl.core.types.dsl.BooleanExpression;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;import javax.annotation.Nullable;import static org.junit.jupiter.api.Assertions.*;
@SpringBootTest
class StudentDSLMapperTest {@Autowiredprivate StudentDSLMapper mapper;@Testvoid test1() {QStudent student = QStudent.student;BooleanExpression eq = student.id.eq(7L);Iterable<Student> all = mapper.findAll(eq);System.out.println(all);}/*** 查询名称范围(in)* id>大于* 地址精确**/@Testvoid name() {QStudent student = QStudent.student;BooleanExpression a = student.id.in(3, 7, 9).and(student.name.startsWith("a")).and(student.grade.gt(0));Iterable<Student> all = mapper.findAll(a);System.out.println(all);}
}

原生态

package com.jmj.springDataApp.mapper;import com.jmj.springDataApp.pojo.QStudent;
import com.jmj.springDataApp.pojo.Student;
import com.querydsl.core.Tuple;
import com.querydsl.jpa.impl.JPAQuery;
import com.querydsl.jpa.impl.JPAQueryFactory;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;import javax.persistence.EntityManager;
import javax.persistence.EntityTransaction;
import javax.persistence.PersistenceContext;
import java.util.List;@SpringBootTest
public class EntityManagerTest {@PersistenceContextprivate EntityManager em;@Testvoid test1() {JPAQueryFactory jpaQueryFactory = new JPAQueryFactory(em);QStudent student = QStudent.student;JPAQuery<Tuple> b = jpaQueryFactory.select(student.id, student.name, student.grade).from(student).where(student.id.gt(3), student.name.contains("b")).orderBy(student.id.desc()).limit(3);List<Tuple> fetch = b.fetch();for (Tuple tuple : fetch) {Long aLong = tuple.get(student.id);String s = tuple.get(student.name);Integer integer = tuple.get(student.grade);System.out.println(aLong+s+integer);}}@Testvoid test2() {JPAQueryFactory jpaQueryFactory = new JPAQueryFactory(em);QStudent student = QStudent.student;JPAQuery<Long> b = jpaQueryFactory.select(student.id.sum()).from(student).where(student.id.gt(3), student.name.contains("b")).orderBy(student.id.desc()).limit(3);List<Long> fetch = b.fetch();for (Long aLong : fetch) {System.out.println(aLong);}}}