QueryDSL产生JPQL而不是SQL的SQLDIALECT

Question

试图让QueryDSL了低于本地SQL是Spring启动POM片断

<parent> 
     <groupId>org.springframework.boot</groupId> 
     <artifactId>spring-boot-starter-parent</artifactId> 
     <version>1.3.3.RELEASE</version> 
     <relativePath/> <!-- lookup parent from repository --> 
    </parent> 

    <properties> 
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> 
     <java.version>1.7</java.version> 
     <querydsl.version>4.0.1</querydsl.version> 
    </properties> 

    <dependencies> 
     <dependency> 
      <groupId>org.springframework.boot</groupId> 
      <artifactId>spring-boot-starter</artifactId> 
     </dependency> 
     <dependency> 
      <groupId>org.springframework.boot</groupId> 
      <artifactId>spring-boot-starter-jdbc</artifactId> 
     </dependency> 
     <dependency> 
      <groupId>org.hibernate</groupId> 
      <artifactId>hibernate-validator</artifactId> 
     </dependency> 
     <dependency> 
      <groupId>org.hsqldb</groupId> 
      <artifactId>hsqldb</artifactId> 
      <scope>runtime</scope> 
     </dependency> 
     <dependency> 
      <groupId>com.querydsl</groupId> 
      <artifactId>querydsl-sql</artifactId> 
      <version>${querydsl.version}</version> 
     </dependency> 
     <dependency> 
      <groupId>com.querydsl</groupId> 
      <artifactId>querydsl-sql-codegen</artifactId> 
      <version>${querydsl.version}</version> 
      <scope>provided</scope> 
     </dependency> 
    </dependencies> 

    <build> 
     <plugins> 

      ..... 

      <plugin> 
       <groupId>com.querydsl</groupId> 
       <artifactId>querydsl-maven-plugin</artifactId> 
       <version>${querydsl.version}</version> 
       <executions> 
        <execution> 
         <goals> 
          <goal>export</goal> 
         </goals> 
        </execution> 
       </executions> 
       <configuration> 
        <jdbcDriver>org.hsqldb.jdbc.JDBCDriver</jdbcDriver> 
        <jdbcUrl>jdbc:hsqldb:file:${project.basedir}/db/init;files_readonly=true</jdbcUrl> 
        <jdbcUser>sa</jdbcUser> 
        <schemaPattern>PUBLIC</schemaPattern> 
        <packageName>com.example.domain</packageName> 
        <targetFolder>${project.basedir}/src/generated/java</targetFolder> 
       </configuration> 
       <dependencies> 
        <dependency> 
         <groupId>org.hsqldb</groupId> 
         <artifactId>hsqldb</artifactId> 
         <version>2.2.4</version> 
        </dependency> 
        <dependency> 
         <groupId>ch.qos.logback</groupId> 
         <artifactId>logback-classic</artifactId> 
         <version>1.1.5</version> 
        </dependency> 
       </dependencies> 
      </plugin> 

     </plugins> 
    </build> 

代码执行查询

void test() throws Exception { 
    QCustomer customer = QCustomer.customer; 
    System.out.println(dataSource.getConnection().getMetaData().getDatabaseProductName()); 
    SQLTemplates dialect = SQLTemplates.DEFAULT; 
    SQLQuery query = new SQLQuery(dataSource.getConnection(), dialect); 
    System.out.println(query.from(customer.count()).fetch()); 
} 

的执行结果SQLException作为库生成JPQL（或HQL）而不是原生SQL

Exception in thread "main" com.querydsl.core.QueryException: Caught SQLSyntaxErrorException for 
from count(CUSTOMER.ID) 
    at com.querydsl.sql.DefaultSQLExceptionTranslator.translate(DefaultSQLExceptionTranslator.java:50) 
    at com.querydsl.sql.Configuration.translate(Configuration.java:451) 
    at com.querydsl.sql.AbstractSQLQuery.fetch(AbstractSQLQuery.java:399) 
    at com.example.DemoApplication$Test.test(DemoApplication.java:55) 
    at com.example.DemoApplication.main(DemoApplication.java:36) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) 
    at java.lang.reflect.Method.invoke(Method.java:497) 
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144) 
Caused by: java.sql.SQLSyntaxErrorException: unexpected token: FROM 

Answer 1

我们应该使用

query.select(customer.count()) 
    .from(customer) 
    .fetch() 

和QueryDSL 4.X及更高版本（最新版本）是指http://www.querydsl.com/static/querydsl/latest/reference/html/ch02s03.html#d0e1145