为什么要使用查询语言?对于任何复杂的API来说 - 通过非常简单的字段搜索 / 过滤资源是不够的。查询语言更灵活,允许您精确过滤所需的资源。
Query DSL配置
我们需要将以下依赖项添加到pom.xml:
<dependency>
<groupId>com.querydsl</groupId>
<artifactId>querydsl-apt</artifactId>
<version>4.1.4</version>
</dependency>
<dependency>
<groupId>com.querydsl</groupId>
<artifactId>querydsl-jpa</artifactId>
<version>4.1.4</version>
</dependency>
我们还需要配置APT - Annotation处理工具 - 插件如下:
<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.mysema.query.apt.jpa.JPAAnnotationProcessor</processor>
</configuration>
</execution>
</executions>
</plugin>
MyUser Entity
接下来 - 让我们看一下我们将在Search API中使用的 MyUser 实体:
@Entity
public class MyUser {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String firstName;
private String lastName;
private String email;
private int age;
}
使用PathBuilder自定义Predicate
根据一些任意约束创建一个自定义Predicate。
我们在这里使用PathBuilder而不是自动生成的Q类型,因为我们需要动态创建路径以获得更抽象的用法:
public class MyUserPredicate {
private SearchCriteria criteria;
public BooleanExpression getPredicate() {
PathBuilder<MyUser> entityPath = new PathBuilder<>(MyUser.class, "user");
if (isNumeric(criteria.getValue().toString())) {
NumberPath<Integer> path = entityPath.getNumber(criteria.getKey(), Integer.class);
int value = Integer.parseInt(criteria.getValue().toString());
switch (criteria.getOperation()) {
case ":":
return path.eq(value);
case ">":
return path.goe(value);
case "<":
return path.loe(value);
}
}
else {
StringPath path = entityPath.getString(criteria.getKey());
if (criteria.getOperation().equalsIgnoreCase(":")) {
return path.containsIgnoreCase(criteria.getValue().toString());
}
}
return null;
}
}
请注意Predicate的实现是通常如何处理多种类型的操作。这是因为查询语言根据定义是一种开放式语言,您可以使用任何支持的操作对任何字段进行过滤。
为了表示这种开放式过滤标准,我们使用了一个简单但非常灵活的实现 - SearchCriteria:
public class SearchCriteria {
private String key;
private String operation;
private Object value;
}
- key:用于保存字段名称 - 例如:firstName,age,...等。
- operation:用于保持操作 - 例如:Equality,less,...等。
- value:用于保存字段值 - 例如:john,25,...等。
MyUserRepository
现在 - 让我们来看看我们的MyUserRepository。
我们需要MyUserRepository来扩展QueryDslPredicateExecutor,以便我们以后可以使用Predicates来过滤搜索结果:
public interface MyUserRepository extends JpaRepository<MyUser, Long>,
QueryDslPredicateExecutor<MyUser>, QuerydslBinderCustomizer<QMyUser> {
@Override
default public void customize(
QuerydslBindings bindings, QMyUser root) {
bindings.bind(String.class)
.first((SingleValueBinding<StringPath, String>) StringExpression::containsIgnoreCase);
bindings.excluding(root.email);
}
}
结合Predicates
接下来让我们看看组合Predicates在结果过滤中使用多个约束。
在以下示例中 - 我们使用构建器 - MyUserPredicatesBuilder - 来组合Predicates:
public class MyUserPredicatesBuilder {
private List<SearchCriteria> params;
public MyUserPredicatesBuilder() {
params = new ArrayList<>();
}
public MyUserPredicatesBuilder with(
String key, String operation, Object value) {
params.add(new SearchCriteria(key, operation, value));
return this;
}
public BooleanExpression build() {
if (params.size() == 0) {
return null;
}
List<BooleanExpression> predicates = new ArrayList<>();
MyUserPredicate predicate;
for (SearchCriteria param : params) {
predicate = new MyUserPredicate(param);
BooleanExpression exp = predicate.getPredicate();
if (exp != null) {
predicates.add(exp);
}
}
BooleanExpression result = predicates.get(0);
for (int i = 1; i < predicates.size(); i++) {
result = result.and(predicates.get(i));
}
return result;
}
}
测试搜索查询
接下来 - 让我们测试一下我们的Search API。
我们将首先使用少数用户初始化数据库 - 准备好这些数据并进行测试:
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = { PersistenceConfig.class })
@Transactional
@Rollback
public class JPAQuerydslIntegrationTest {
@Autowired
private MyUserRepository repo;
private MyUser userJohn;
private MyUser userTom;
@Before
public void init() {
userJohn = new MyUser();
userJohn.setFirstName("John");
userJohn.setLastName("Doe");
userJohn.setEmail("john@doe.com");
userJohn.setAge(22);
repo.save(userJohn);
userTom = new MyUser();
userTom.setFirstName("Tom");
userTom.setLastName("Doe");
userTom.setEmail("tom@doe.com");
userTom.setAge(26);
repo.save(userTom);
}
}
接下来,让我们看看如何查找具有给定姓氏的用户:
@Test
public void givenLast_whenGettingListOfUsers_thenCorrect() {
MyUserPredicatesBuilder builder = new MyUserPredicatesBuilder().with("lastName", ":", "Doe");
Iterable<MyUser> results = repo.findAll(builder.build());
assertThat(results, containsInAnyOrder(userJohn, userTom));
}
现在,让我们看看如何找到具有名字和姓氏的用户:
@Test
public void givenFirstAndLastName_whenGettingListOfUsers_thenCorrect() {
MyUserPredicatesBuilder builder = new MyUserPredicatesBuilder()
.with("firstName", ":", "John").with("lastName", ":", "Doe");
Iterable<MyUser> results = repo.findAll(builder.build());
assertThat(results, contains(userJohn));
assertThat(results, not(contains(userTom)));
}
接下来,让我们看看如何找到具有姓氏和最小年龄的用户
@Test
public void givenLastAndAge_whenGettingListOfUsers_thenCorrect() {
MyUserPredicatesBuilder builder = new MyUserPredicatesBuilder()
.with("lastName", ":", "Doe").with("age", ">", "25");
Iterable<MyUser> results = repo.findAll(builder.build());
assertThat(results, contains(userTom));
assertThat(results, not(contains(userJohn)));
}
接下来,让我们搜索实际不存在的用户:
@Test
public void givenWrongFirstAndLast_whenGettingListOfUsers_thenCorrect() {
MyUserPredicatesBuilder builder = new MyUserPredicatesBuilder()
.with("firstName", ":", "Adam").with("lastName", ":", "Fox");
Iterable<MyUser> results = repo.findAll(builder.build());
assertThat(results, emptyIterable());
}
最后 - 让我们看看如何找到仅给出名字的一部分的MyUser - 如下例所示:
@Test
public void givenPartialFirst_whenGettingListOfUsers_thenCorrect() {
MyUserPredicatesBuilder builder = new MyUserPredicatesBuilder().with("firstName", ":", "jo");
Iterable<MyUser> results = repo.findAll(builder.build());
assertThat(results, contains(userJohn));
assertThat(results, not(contains(userTom)));
}
UserController
最后,让我们将所有内容放在一起并构建REST API。
我们定义了一个UserController,它定义了一个带有“search”参数的简单方法findAll()来传递查询字符串:
@Controller
public class UserController {
@Autowired
private MyUserRepository myUserRepository;
@RequestMapping(method = RequestMethod.GET, value = "/myusers")
@ResponseBody
public Iterable<MyUser> search(@RequestParam(value = "search") String search) {
MyUserPredicatesBuilder builder = new MyUserPredicatesBuilder();
if (search != null) {
Pattern pattern = Pattern.compile("(\w+?)(:|<|>)(\w+?),");
Matcher matcher = pattern.matcher(search + ",");
while (matcher.find()) {
builder.with(matcher.group(1), matcher.group(2), matcher.group(3));
}
}
BooleanExpression exp = builder.build();
return myUserRepository.findAll(exp);
}
}
这是一个快速测试URL示例:
http://localhost:8080/myusers?search=lastName:doe,age>25
回应:
[{
"id":2,
"firstName":"tom",
"lastName":"doe",
"email":"tom@doe.com",
"age":26
}]
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