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。

本文参考链接：https://blog.csdn.net/neweastsun/article/details/78365831

QueryDsl查询mongodb数据2