QueryDsl查询实例

上节已经生成了Query类，本文通过示例说明如何通过Query类实现灵活查询。

示例类及查询类

为了说明示例，这里定义简单的User类，以及依据User类生成的QUser类。

User类：

@Document
public class User {
    

    @Id
    private String id;
    private String name;
    private Integer age;

    // standard getters and setters
}

QUser类：

Query类是通过gradle插件自动生成的。

/**
 * QUser is a Querydsl query type for User
 */
@Generated("com.mysema.query.codegen.EntitySerializer")
public class QUser extends EntityPathBase<User> {
    

    private static final long serialVersionUID = ...;

    public static final QUser user = new QUser("user");

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

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

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

    public QUser(String variable) {
        super(User.class, forVariable(variable));
    }

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

    public QUser(PathMetadata<?> metadata) {
        super(User.class, metadata);
    }
}

QueryDslPredicateExecutor接口

为了启用QueryDsl查询，需要简单继承QueryDslPredicateExecutor接口。

public interface UserRepository extends
  MongoRepository<User, String>, QueryDslPredicateExecutor<User>

Eq

实现值相等查询。

QUser qUser = new QUser("user");
Predicate predicate = qUser.name.eq("Eric");
List<User> users = (List<User>) userRepository.findAll(predicate);

也可以指定多个条件

Predicate nameAndAgeAre = qUser.name.eq("Foo").and(qUser.age.eq(22));

StartingWith and EndingWith

实现字符串开头或结尾的模糊查询。

QUser qUser = new QUser("user");
Predicate predicate = qUser.name.startsWith("A");
List<User> users = (List<User>) userRepository.findAll(predicate);

字符串结尾查询：

QUser qUser = new QUser("user");
Predicate predicate = qUser.name.endsWith("c");
List<User> users = (List<User>) userRepository.findAll(predicate);

Between

实现范围查询

QUser qUser = new QUser("user");
Predicate predicate = qUser.age.between(20, 50);
List<User> users = (List<User>) userRepository.findAll(predicate);

组合查询

实现多个或组条件组合查询,摘录项目中的示例代码如下：

QUser qUser = new QUser("user");
Predicate userCode = qUser.userCode.endsWith("4");
Predicate userName = qUser.userName.endsWith("9").or(qUser.userName.endsWith("8"));

BooleanBuilder example = new BooleanBuilder();
example.and(userCode).or(userName);

List<SysOrg> orgList = (List<SysOrg>)orgDao.findAll(example);

assertThat(orgList,hasSize(3));

测试分页

QSysOrg qSysOrg;
qSysOrg = new QSysOrg("sysOrg");
Predicate predicate = qSysOrg.orgCode.startsWith("tx");

Pageable pageable = PageRequest.of(0,5);

Page<SysOrg> orgList = orgDao.findAll(predicate,pageable);

assertThat(orgList.hasNext(),is(true));
assertThat(orgList.getSize(),is(5));

测试排序

QSysOrg qSysOrg = QSysOrg.sysOrg;
Predicate predicate = qSysOrg.orgCode.startsWith("tx");
OrderSpecifier orderSpecifier = qSysOrg.orgCode.asc();

List<SysOrg> orgList = (List<SysOrg>)orgDao.findAll(predicate,orderSpecifier);
SysOrg org = (SysOrg) orgList.get(0);

assertThat(org.getOrgCode(),is("tx001"));

总结

除了上述方法，还有很多功能强大的方法，如：like，contain等，留给善于探索的读者。