非spring框架下使用querydsl

Querydsl是一个采用API代替拼凑字符串来构造查询语句，可跟 Hibernate 和 JPA 等框架结合使用。网上很多教程都是结合spring JPA框架下使用的教程，本文介绍的是非spring环境下querydsl JPA整合使用。
1、使用eclipse生成jpa实体类，IDEA也能生成同样JPA实体类。

鼠标右键打开JPA Tools工具：

创建数据库链接：

选择那些数据库表需要生成JPA实体类：

关联表生成：

设置实体生成属性：

单个实体属性修改

生成的JPA实体类AdminLog.java

package com.test.db.entity; import java.io.Serializable; import javax.persistence.*; import java.util.Date; /** * The persistent class for the admin_log database table. * */ @Entity @Table(name="admin_log") @NamedQuery(name="AdminLog.findAll", query="SELECT a FROM AdminLog a") public class AdminLog implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy=GenerationType.AUTO) @Column(unique=true, nullable=false) private String id; @Column(name="action_id", length=20) private String actionId; @Column(name="client_ip", length=15) private String clientIp; @Column(name="controller_id", length=20) private String controllerId; @Temporal(TemporalType.TIMESTAMP) @Column(name="create_date") private Date createDate; @Column(name="create_user", length=50) private String createUser; @Column(name="func_name", length=50) private String funcName; @Column(name="module_name", length=50) private String moduleName; @Column(name="right_name", length=50) private String rightName; @Column(length=200) private String url; public AdminLog() { } public String getId() { return this.id; } public void setId(String id) { this.id = id; } public String getActionId() { return this.actionId; } public void setActionId(String actionId) { this.actionId = actionId; } public String getClientIp() { return this.clientIp; } public void setClientIp(String clientIp) { this.clientIp = clientIp; } public String getControllerId() { return this.controllerId; } public void setControllerId(String controllerId) { this.controllerId = controllerId; } public Date getCreateDate() { return this.createDate; } public void setCreateDate(Date createDate) { this.createDate = createDate; } public String getCreateUser() { return this.createUser; } public void setCreateUser(String createUser) { this.createUser = createUser; } public String getFuncName() { return this.funcName; } public void setFuncName(String funcName) { this.funcName = funcName; } public String getModuleName() { return this.moduleName; } public void setModuleName(String moduleName) { this.moduleName = moduleName; } public String getRightName() { return this.rightName; } public void setRightName(String rightName) { this.rightName = rightName; } public String getUrl() { return this.url; } public void setUrl(String url) { this.url = url; } }

2、生成querydsl查询类
maven pom.xml文件

<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/maven-v4_0_0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.test.db</groupId> <artifactId>dbtest</artifactId> <packaging>jar</packaging> <version>1.0-SNAPSHOT</version> <name>dbtest</name> <url>http://maven.apache.org</url> <properties> <querydsl.version>4.2.1</querydsl.version> </properties> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>3.8.1</version> <scope>test</scope> </dependency> <dependency> <groupId>com.querydsl</groupId> <artifactId>querydsl-sql</artifactId> <version>${querydsl.version}</version> </dependency> <dependency> <groupId>com.querydsl</groupId> <artifactId>querydsl-apt</artifactId> <version>${querydsl.version}</version> </dependency> <dependency> <groupId>com.querydsl</groupId> <artifactId>querydsl-jpa</artifactId> <version>${querydsl.version}</version> </dependency> <dependency> <groupId>com.querydsl</groupId> <artifactId>querydsl-sql-codegen</artifactId> <version>${querydsl.version}</version> <scope>provided</scope> </dependency> <dependency> <groupId>org.eclipse.persistence</groupId> <artifactId>org.eclipse.persistence.jpa</artifactId> <version>2.6.0</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-log4j12</artifactId> <version>1.6.1</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.11</version> </dependency> <dependency> <groupId>com.alibaba</groupId> <artifactId>druid</artifactId> <version>1.1.10</version> </dependency> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-entitymanager</artifactId> <version>5.4.0.Final</version> </dependency> </dependencies> <build> <plugins> <!-- 生成jpa实体插件 --> <plugin> <groupId>com.querydsl</groupId> <artifactId>querydsl-maven-plugin</artifactId> <version>${querydsl.version}</version> <executions> <execution> <phase>generate-sources</phase> <goals> <goal>jpa-export</goal> </goals> <configuration> <targetFolder>${project.basedir}/target/generated-sources/java</targetFolder> <packages>com.test.db.entity</packages> </configuration> </execution> </executions> </plugin> <!-- 生成jpa实体插件 --> <!-- <plugin> <groupId>com.mysema.maven</groupId> <artifactId>apt-maven-plugin</artifactId> <version>1.1.3</version> <executions> <execution> <goals> <goal>process</goal> </goals> <configuration> <outputDirectory>target/generated-sources/java</outputDirectory> <processor>com.querydsl.apt.jpa.JPAAnnotationProcessor</processor> </configuration> </execution> </executions> </plugin> --> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>3.1</version> <configuration> <source>1.8</source> <target>1.8</target> <encoding>UTF-8</encoding> </configuration> </plugin> </plugins> </build> </project>

执行命令mvn compile或mvn eclipse:eclipse生成jpa实体对应的querydsl查询类

AdminLog.java对应的querydsl对应查询类

package com.test.db.entity; import static com.querydsl.core.types.PathMetadataFactory.*; import com.querydsl.core.types.dsl.*; import com.querydsl.core.types.PathMetadata; import javax.annotation.Generated; import com.querydsl.core.types.Path; /** * QAdminLog is a Querydsl query type for AdminLog */ @Generated("com.querydsl.codegen.EntitySerializer") public class QAdminLog extends EntityPathBase<AdminLog> { private static final long serialVersionUID = 392071999L; public static final QAdminLog adminLog = new QAdminLog("adminLog"); public final StringPath actionId = createString("actionId"); public final StringPath clientIp = createString("clientIp"); public final StringPath controllerId = createString("controllerId"); public final DateTimePath<java.util.Date> createDate = createDateTime("createDate", java.util.Date.class); public final StringPath createUser = createString("createUser"); public final StringPath funcName = createString("funcName"); public final StringPath id = createString("id"); public final StringPath moduleName = createString("moduleName"); public final StringPath rightName = createString("rightName"); public final StringPath url = createString("url"); public QAdminLog(String variable) { super(AdminLog.class, forVariable(variable)); } public QAdminLog(Path<? extends AdminLog> path) { super(path.getType(), path.getMetadata()); } public QAdminLog(PathMetadata metadata) { super(AdminLog.class, metadata); } } 

3、查询例子

JPA持久化META-INF\persistence.xml配置文件，EntityManagerFactory创建实例时，需要读取该配置文件：

<?xml version="1.0" encoding="UTF-8"?> <persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd" version="2.0"> <persistence-unit name="jpa" transaction-type="RESOURCE_LOCAL"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <properties> <!-- .MySQLInnoDBDialect --> <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL8Dialect"/> <property name="javax.persistence.jdbc.driver" value="com.mysql.cj.jdbc.Driver" /> <property name="javax.persistence.jdbc.url" value="jdbc:mysql://127.0.0.1:3306/yiiboot?useUnicode=true&amp;characterEncoding=UTF-8&amp;serverTimezone=Asia/Shanghai&amp;useSSL=true" /> <property name="javax.persistence.jdbc.user" value="root" /> <property name="javax.persistence.jdbc.password" value="123" /> <property name="connection.provider_class" value="com.alibaba.druid.support.hibernate.DruidConnectionProvider" /> <!-- 配置初始化大小、最小、最大 --> <property name="initialSize" value="1" /> <property name="minIdle" value="1" /> <property name="maxActive" value="20" /> <!-- 配置获取连接等待超时的时间 --> <property name="maxWait" value="60000" /> <!-- 配置间隔多久才进行一次检测，检测需要关闭的空闲连接，单位是毫秒 --> <property name="timeBetweenEvictionRunsMillis" value="60000" /> <!-- 配置一个连接在池中最小生存的时间，单位是毫秒 --> <property name="minEvictableIdleTimeMillis" value="300000" /> </properties> </persistence-unit> </persistence>

测试代码

package com.test.db.main; import java.util.List; import javax.persistence.EntityManagerFactory; import javax.persistence.Persistence; import com.querydsl.jpa.impl.JPAQueryFactory; import com.test.db.entity.AdminModule; import com.test.db.entity.QAdminModule; public class JpaTest { public static void main(String[] args) throws Exception{ String persistenceUnitName = "jpa"; EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory(persistenceUnitName); JPAQueryFactory queryFactory = new JPAQueryFactory(entityManagerFactory.createEntityManager()); QAdminModule adminModule = QAdminModule.adminModule; List<AdminModule> list = queryFactory.selectFrom(adminModule).fetch(); list.forEach(module->{ System.out.println(module.getId() + "," + module.getDisplayLabel() + "," + module.getCreateDate()); }); } } 

querydsl官方文档：http://www.querydsl.com/static/querydsl/latest/reference/html/ch02.html#jpa_integration
java类库：https://www.21doc.net/java/awesomejava#database