java - Spring Boot QueryDsl 返回由 : java. lang.UnsupportedOperationException 引起:null

Question

代码如下

    QContinent continent = QContinent.continent;

    JPAQuery query = new JPAQuery(entityManager);


    query.from(continent).where(continent.name.eq("www"));
    List<Object> fetch = query.fetch();

    System.err.println("===" + fetch);

这返回
引起:java.lang.UnsupportedOperationException:null
在 java.util.Collections$UnmodifiableMap.put(Collections.java:1457) ~[na:1.8.0_191]
在 com.querydsl.jpa.JPQLSerializer.visitConstant(JPQLSerializer.java:327) ~[querydsl-jpa-4.2.1.jar:na]
在 com.querydsl.core.support.SerializerBase.visit(SerializerBase.java:221) ~[querydsl-core-4.3.1.jar:na]
在 com.querydsl.core.support.SerializerBase.visit(SerializerBase.java:36) ~[querydsl-core-4.3.1.jar:na]
在 com.querydsl.core.types.ConstantImpl.accept(ConstantImpl.java:140) ~[querydsl-core-4.3.1.jar:na]

Answer 1

正如@user3388770 所建议的，原因是版本不匹配。一般来说，在您的 pom.xml/build.gradle不要为依赖项指定版本，Spring 已经提供了，除非您出于某种原因确实需要它。
您可以在此处找到使用的/兼容的依赖项:https://docs.spring.io/spring-boot/docs/2.3.1.RELEASE/reference/html/appendix-dependency-versions.html (根据您的Spring版本更改版本)
如果出现错误，您的依赖项应如下所示( build.gradle ):

plugins {
    id "org.springframework.boot" version "2.3.1.RELEASE"
    id 'io.spring.dependency-management' version '1.0.9.RELEASE'
    ...
}

apply plugin: 'org.springframework.boot'
apply plugin: 'io.spring.dependency-management'
...

dependencies {
   annotationProcessor(
            ...
            //some put a version below before ":jpa"; dont.
            "com.querydsl:querydsl-apt::jpa"
            ...
    )

    //just an example without version numbers as they are delivered with spring boot automatically
    compile "org.springframework.boot:spring-boot-starter-web"
    compile "org.springframework.boot:spring-boot-actuator"
    ...
    compile group: 'org.apache.httpcomponents', name: 'httpclient'
    compile 'org.thymeleaf.extras:thymeleaf-extras-java8time'

    //but most importantly this below 
    compile "com.querydsl:querydsl-jpa"
}