springjpa（三）QueryDsl

（一）QueryDsl簡介

這邊簡介我就不從各大網站的文章中copy過來了，這邊給個官網的中文翻譯傳送門：http://books.aying.org/querydsl_zh_CN/Introduction.html

（二）引入QueryDsl

2.1 依賴

        <dependency>
            <groupId>com.querydsl</groupId>
            <artifactId>querydsl-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>com.querydsl</groupId>
            <artifactId>querydsl-apt</artifactId>
            <scope>provided</scope>
        </dependency>

2.2 plugin

　　　　　　　<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>

JPAAnnotationProcessor 查找帶有 javax.persistence.Entity 注解的領域類型並為其生成查詢類型。簡單來說，比如有個Student的entity，運行clean install 會在項目的target/generated-sources/java 目錄下將生成QStudent，這個QStudent就是查詢類型類。

（三）實體 Student類

@Table(name = "student")
@Entity
public class Student {

    @Id
    @GeneratedValue(
            strategy = GenerationType.IDENTITY
    )
    private long id;

    private String name;

    private int age;

    private long schoolId;

    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 getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public long getSchoolId() {
        return schoolId;
    }

    public void setSchoolId(Long schoolId) {
        this.schoolId = schoolId;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", schoolId=" + schoolId +
                '}';
    }
}

　運行mvn clean install后生成的QStudent

@Generated("com.querydsl.codegen.EntitySerializer")
public class QStudent extends EntityPathBase<Student> {

    private static final long serialVersionUID = -5814978L;

    public static final QStudent student = new QStudent("student");

    public final NumberPath<Integer> age = createNumber("age", Integer.class);

    public final NumberPath<Long> id = createNumber("id", Long.class);

    public final StringPath name = createString("name");

    public final NumberPath<Long> schoolId = createNumber("schoolId", Long.class);

    public QStudent(String variable) {
        super(Student.class, forVariable(variable));
    }

    public QStudent(Path<? extends Student> path) {
        super(path.getType(), path.getMetadata());
    }

    public QStudent(PathMetadata metadata) {
        super(Student.class, metadata);
    }

}

（四）查詢

4.0 QueryDslTest測試類

@RunWith(SpringRunner.class)
@SpringBootTest
public class QueryDslTest {

    @Autowired
    @PersistenceContext
    private EntityManager entityManager;

    private JPAQueryFactory queryFactory;

    @Before
    public void init() {
        queryFactory = new JPAQueryFactory(entityManager);
    }
}

4.1 簡單查詢

@Test
    public void selectStudent(){
        QStudent qStudent = QStudent.student;
        List<Student> students = queryFactory.selectFrom(qStudent).fetch();
        System.out.println(students);
    }

4.2 單表條件查詢

@Test
public void selectStudentWithWhere() {
    QStudent qStudent = QStudent.student;
    //單表單條件查詢
    List<Student> students = queryFactory.selectFrom(qStudent).where(qStudent.age.goe(2)).fetch();
    //單表多條件and查詢
    List<Student> studentList = queryFactory.selectFrom(qStudent).where(qStudent.age.goe(2).and(qStudent.name.eq("vincent"))).fetch();
    //單表多條件or查詢
    List<Student> list = queryFactory.selectFrom(qStudent).where(qStudent.age.goe(20).or(qStudent.name.eq("vincent"))).fetch();
    //單表排序分頁查詢
    List<Student> list1 = queryFactory.selectFrom(qStudent).offset(1).limit(3).orderBy(qStudent.id.desc()).fetch();
    System.out.println(students);
    System.out.println(studentList);
    System.out.println(list);
    System.out.println(list1);
}

4.3 多表查詢

　　 @Test
    public void selectStudent1() {
        QStudent qStudent = QStudent.student;
        QSchool qSchool = QSchool.school;
        List<Student> students = queryFactory.select(qStudent).from(qSchool, qStudent).where(qSchool.id.eq(qStudent.schoolId)).fetch();
        System.out.println(students);
    }

　以上查詢的結果只是student的表的值，比如我現在關心學校名稱，那么這樣子就不能得到，用下面的做法可以得到你想要的值

    @Test
    public void selectStudent2() {
        QStudent qStudent = QStudent.student;
        QSchool qSchool = QSchool.school;
        List<Tuple> students = queryFactory.select(qStudent.age, qStudent.name, qSchool.name).from(qSchool, qStudent).where(qSchool.id.eq(qStudent.schoolId)).fetch();
        List<Map<String, Object>> maps = students.stream().map(tuple -> {
            Map<String, Object> map = new HashMap<>();
            map.put("studentName", tuple.get(qStudent.name));
            map.put("age", tuple.get(qStudent.age));
            map.put("schoolName", tuple.get(qSchool.name));
            return map;
        }).collect(Collectors.toList());
        System.out.println(maps);
    }

　4.4 leftjoin查詢

    @Test
    public void selectStudent3() {
        QStudent qStudent = QStudent.student;
        QSchool qSchool = QSchool.school;
        List<Student> students = queryFactory.select(qStudent)
                .from(qStudent)
                .leftJoin(qSchool)
                .on(qStudent.schoolId.eq(qSchool.id))
                .fetch();
        System.out.println(students);
    }

　這段代碼本身是沒有問題的，不過按照之前的配置運行起來將會報以下錯誤，如何解決我在后面另寫一個文章。

2018-09-06 10:25:25.678 ERROR 4742 --- [           main] o.h.hql.internal.ast.ErrorCounter        :  Path expected for join!
2018-09-06 10:25:25.686 ERROR 4742 --- [           main] o.h.hql.internal.ast.ErrorCounter        :  Path expected for join!

antlr.SemanticException: Path expected for join!
	at org.hibernate.hql.internal.ast.HqlSqlWalker.createFromJoinElement(HqlSqlWalker.java:368) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
	at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.joinElement(HqlSqlBaseWalker.java:3912) [hibernate-core-5.0.12.Final.jar:5.0.12.Final]
	at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromElement(HqlSqlBaseWalker.java:3698) [hibernate-core-5.0.12.Final.jar:5.0.12.Final]
	at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromElementList(HqlSqlBaseWalker.java:3576) [hibernate-core-5.0.12.Final.jar:5.0.12.Final]
	at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.fromClause(HqlSqlBaseWalker.java:716) [hibernate-core-5.0.12.Final.jar:5.0.12.Final]
	at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:572) [hibernate-core-5.0.12.Final.jar:5.0.12.Final]
	at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:309) [hibernate-core-5.0.12.Final.jar:5.0.12.Final]
	at org.hibernate.hql.internal.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:257) [hibernate-core-5.0.12.Final.jar:5.0.12.Final]
	at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:262) [hibernate-core-5.0.12.Final.jar:5.0.12.Final]
	at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:190) [hibernate-core-5.0.12.Final.jar:5.0.12.Final]
	at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:142) [hibernate-core-5.0.12.Final.jar:5.0.12.Final]
	at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:115) [hibernate-core-5.0.12.Final.jar:5.0.12.Final]
	at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:76) [hibernate-core-5.0.12.Final.jar:5.0.12.Final]
	at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:150) [hibernate-core-5.0.12.Final.jar:5.0.12.Final]
	at org.hibernate.internal.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:302) [hibernate-core-5.0.12.Final.jar:5.0.12.Final]
	at org.hibernate.internal.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:240) [hibernate-core-5.0.12.Final.jar:5.0.12.Final]
	at org.hibernate.internal.SessionImpl.createQuery(SessionImpl.java:1894) [hibernate-core-5.0.12.Final.jar:5.0.12.Final]
	at org.hibernate.jpa.spi.AbstractEntityManagerImpl.createQuery(AbstractEntityManagerImpl.java:291) [hibernate-entitymanager-5.0.12.Final.jar:5.0.12.Final]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_144]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_144]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_144]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_144]
	at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:347) [spring-orm-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at com.sun.proxy.$Proxy91.createQuery(Unknown Source) [na:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_144]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_144]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_144]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_144]
	at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:298) [spring-orm-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at com.sun.proxy.$Proxy91.createQuery(Unknown Source) [na:na]
	at com.querydsl.jpa.impl.AbstractJPAQuery.createQuery(AbstractJPAQuery.java:101) [querydsl-jpa-4.1.4.jar:na]
	at com.querydsl.jpa.impl.AbstractJPAQuery.createQuery(AbstractJPAQuery.java:94) [querydsl-jpa-4.1.4.jar:na]
	at com.querydsl.jpa.impl.AbstractJPAQuery.fetch(AbstractJPAQuery.java:201) [querydsl-jpa-4.1.4.jar:na]
	at com.vincent.QueryDslTest.selectStudent4(QueryDslTest.java:129) [test-classes/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_144]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_144]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_144]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_144]
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50) [junit-4.12.jar:4.12]
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) [junit-4.12.jar:4.12]
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47) [junit-4.12.jar:4.12]
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) [junit-4.12.jar:4.12]
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26) [junit-4.12.jar:4.12]
	at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75) [spring-test-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86) [spring-test-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84) [spring-test-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325) [junit-4.12.jar:4.12]
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:252) [spring-test-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94) [spring-test-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) [junit-4.12.jar:4.12]
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) [junit-4.12.jar:4.12]
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) [junit-4.12.jar:4.12]
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) [junit-4.12.jar:4.12]
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) [junit-4.12.jar:4.12]
	at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61) [spring-test-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70) [spring-test-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363) [junit-4.12.jar:4.12]
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191) [spring-test-4.3.13.RELEASE.jar:4.3.13.RELEASE]
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137) [junit-4.12.jar:4.12]
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68) [junit-rt.jar:na]
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47) [junit-rt.jar:na]
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242) [junit-rt.jar:na]
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70) [junit-rt.jar:na]


java.lang.IllegalArgumentException: org.hibernate.hql.internal.ast.QuerySyntaxException: Path expected for join! [select student
from com.vincent.model.Student student
  left join School school with student.schoolId = school.id
where student.name = ?1]

	at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1679)
	at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1602)
	at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1608)
	at org.hibernate.jpa.spi.AbstractEntityManagerImpl.createQuery(AbstractEntityManagerImpl.java:294)
	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:498)
	at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:347)
	at com.sun.proxy.$Proxy91.createQuery(Unknown Source)
	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:498)
	at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:298)
	at com.sun.proxy.$Proxy91.createQuery(Unknown Source)
	at com.querydsl.jpa.impl.AbstractJPAQuery.createQuery(AbstractJPAQuery.java:101)
	at com.querydsl.jpa.impl.AbstractJPAQuery.createQuery(AbstractJPAQuery.java:94)
	at com.querydsl.jpa.impl.AbstractJPAQuery.fetch(AbstractJPAQuery.java:201)
	at com.vincent.QueryDslTest.selectStudent4(QueryDslTest.java:129)
	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:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
	at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
	at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:252)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
	at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: org.hibernate.hql.internal.ast.QuerySyntaxException: Path expected for join! [select student
from com.vincent.model.Student student
  left join School school with student.schoolId = school.id
where student.name = ?1]
	at org.hibernate.hql.internal.ast.QuerySyntaxException.convert(QuerySyntaxException.java:74)
	at org.hibernate.hql.internal.ast.ErrorCounter.throwQueryException(ErrorCounter.java:91)
	at org.hibernate.hql.internal.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:268)
	at org.hibernate.hql.internal.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:190)
	at org.hibernate.hql.internal.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:142)
	at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:115)
	at org.hibernate.engine.query.spi.HQLQueryPlan.<init>(HQLQueryPlan.java:76)
	at org.hibernate.engine.query.spi.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:150)
	at org.hibernate.internal.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:302)
	at org.hibernate.internal.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:240)
	at org.hibernate.internal.SessionImpl.createQuery(SessionImpl.java:1894)
	at org.hibernate.jpa.spi.AbstractEntityManagerImpl.createQuery(AbstractEntityManagerImpl.java:291)
	... 45 more

　　

（五）更新

在Querydsl JPA中，更新語句是簡單的 update-set/where-execute 形式。

execute()執行后返回的是被更新的實體的數量。

@Test
public void testUpdate() {
    QStudent qStudent = QStudent.student;
    Long result = queryFactory.update(qStudent)
            .set(qStudent.name, "haha")
            .where(qStudent.id.eq(111L)).execute();
    assertThat(result,equalTo(1L));
}

　這段代碼運行后會報錯，錯誤如下

javax.persistence.TransactionRequiredException: Executing an update/delete query

	at org.hibernate.jpa.spi.AbstractQueryImpl.executeUpdate(AbstractQueryImpl.java:54)
	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:498)
	at org.springframework.orm.jpa.SharedEntityManagerCreator$DeferredQueryInvocationHandler.invoke(SharedEntityManagerCreator.java:372)
	at com.sun.proxy.$Proxy102.executeUpdate(Unknown Source)
	at com.querydsl.jpa.impl.JPAUpdateClause.execute(JPAUpdateClause.java:77)
	at com.vincent.QueryDslTest.testUpdate(QueryDslTest.java:156)
	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:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
	at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
	at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:252)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
	at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

原因是jpa的update和delete需要加上@Transactional注解，這個細節很重要

可執行版本如下

    @Test
    @Transactional
    public void testUpdate() {
        QStudent qStudent = QStudent.student;
        Long result = queryFactory.update(qStudent)
                .set(qStudent.name, "haha")
                .where(qStudent.id.eq(111L)).execute();
        assertThat(result,equalTo(1L));
    }

　　

（六）刪除　

　刪除語句是簡單的 delete-where-execute 形式。

    @Test
    @Transactional
    public void testDelete() {
        QStudent qStudent = QStudent.student;
        //刪除指定的一個
        Long result = queryFactory.delete(qStudent)
                .where(qStudent.id.eq(111L))
                .execute();
        assertThat(result, equalTo(1L));
        //刪除所有
        Long totalResult = queryFactory.delete(qStudent)
                .execute();
        System.out.println(totalResult);
    }