Spring?Data?JPA系列QueryByExampleExecutor使用詳解
1、QueryByExampleExecutor用法
在前面章節(jié)中,我們介紹了DMQ 和 @Query兩種查詢方法,除此之外,還有QueryByExampleExecutor查詢方法。
1.1 介紹
QueryByExampleExecutor是一種用戶友好的查詢技術(shù),具有簡單的接口,它允許動(dòng)態(tài)創(chuàng)建,并且不需要填寫包含字段名稱的查詢。
1.2 QueryByExampleExecutor接口
public interface QueryByExampleExecutor<T> { // 根據(jù)實(shí)體查詢條件、查找一個(gè)對(duì)象 <S extends T> Optional<S> findOne(Example<S> example); // 根據(jù)實(shí)體查詢條件、查詢一批對(duì)象 <S extends T> Iterable<S> findAll(Example<S> example); // 根據(jù)實(shí)體查詢條件并排序、查詢一批對(duì)象 <S extends T> Iterable<S> findAll(Example<S> example, Sort sort); // 根據(jù)實(shí)體查詢條件并分頁,查詢一批對(duì)象 <S extends T> Page<S> findAll(Example<S> example, Pageable pageable); // 根據(jù)實(shí)體查詢條件、查詢符合條件的對(duì)象個(gè)數(shù) <S extends T> long count(Example<S> example); // 根據(jù)實(shí)體查詢條件、判斷是否有符合條件的對(duì)象 <S extends T> boolean exists(Example<S> example); // 根據(jù)實(shí)體查詢條件、判斷是否有符合條件的對(duì)象 <S extends T, R> R findBy(Example<S> example, Function<FluentQuery.FetchableFluentQuery<S>, R> queryFunction); }
1.3 QueryByExampleExecutor實(shí)踐
第一步 :創(chuàng)建User實(shí)體和UserAddress實(shí)體
// User表 @Data @Entity @NoArgsConstructor @AllArgsConstructor @Builder @ToString(exclude = "address") public class User { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Integer id; private String name; private String email; private Integer age; private LocalDateTime createTime; private LocalDateTime updateTime; @OneToMany(mappedBy = "user",fetch = FetchType.LAZY) private List<UserAddress> address; } // Address表 @Entity @Data @Builder @AllArgsConstructor @NoArgsConstructor @ToString(exclude = "user") public class UserAddress { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; private String address; @ManyToOne(cascade = CascadeType.ALL) private User user; }
第二步: 編寫DAO層,JpaRepository已經(jīng)繼承QueryByExampleExceutor
public interface UserAddressRepo extends JpaRepository<UserAddress,Integer> { }
第三步:測試
@Test public void test01 () { User user = User.builder() .name("jack") .email("123456@126.com") .age(20) .build(); userAddressRepo.saveAll(Lists.newArrayList(UserAddress.builder() .address("shanghai").user(user).build(),UserAddress.builder() .address("beijing").user(user).build())); } @Test public void testQBEE() throws JsonProcessingException { User user = User.builder() .name("jack") .age(20) .email("12345") .build(); UserAddress userAddress = UserAddress.builder() .address("shanghai") .user(user) .build(); ObjectMapper objectMapper = new ObjectMapper(); // 創(chuàng)建匹配器,構(gòu)建動(dòng)態(tài)查詢條件 ExampleMatcher exampleMatcher = ExampleMatcher.matching() .withMatcher("user.email",ExampleMatcher.GenericPropertyMatchers.startsWith()) .withMatcher("address",ExampleMatcher.GenericPropertyMatchers.startsWith()); Page<UserAddress> u = userAddressRepo.findAll(Example.of(userAddress,exampleMatcher), PageRequest.of(0,2)); System.out.println(objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(u)); }
一開始寫這個(gè)代碼的時(shí)候,我也比較懵逼, Example是什么?ExampleMatcher是什么? 下面我一一介紹。
1.4 Example語法詳解
首先:我們先看Example的源碼
public interface Example<T> { static <T> Example<T> of(T probe) { return new TypedExample<>(probe, ExampleMatcher.matching()); } static <T> Example<T> of(T probe, ExampleMatcher matcher) { return new TypedExample<>(probe, matcher); } T getProbe(); ExampleMatcher getMatcher(); @SuppressWarnings("unchecked") default Class<T> getProbeType() { return (Class<T>) ProxyUtils.getUserClass(getProbe().getClass()); } }
- probe:實(shí)際實(shí)體類,即查詢條件的封裝類(又可以理解為查詢條件參數(shù))
- ExampleMatcher :匹配器,匹配特定字段的匹配規(guī)則。
- Example:由probe 和 ExampleMatcher租車,由于創(chuàng)建查詢,即組合查詢參數(shù)和參數(shù)的匹配規(guī)則。
創(chuàng)建Example的兩個(gè)方法 :
- static Example of(T probe):需要一個(gè)實(shí)體參數(shù),即查詢條件。而里面的ExampleMatcher采用默認(rèn)的ExamoleMatcher.matching(); 表示忽略NULL,所有字段采用精準(zhǔn)匹配
- static Example of(T probe, ExampleMatcher matcher):需要兩個(gè)參數(shù)構(gòu)建Example,也就表示ExampleMatcher自由組合規(guī)則,正如我們上面的測試用例里面的代碼一樣。
1.5 ExampleMatcher語法分析
上圖是ExampleMatcher向外暴露的方法,我們只要關(guān)心返回值為ExampleMatcher類型的方法。
其中有三個(gè)方法我們需要注意一下:
static ExampleMatcher matching() { return matchingAll(); } static ExampleMatcher matchingAll() { return new TypedExampleMatcher().withMode(MatchMode.ALL); }
上述的這兩種方法表達(dá)的意思是一樣的。兩者采用的都是MatcheMode.ALL的模式,即AND模式,生成的SQL如下:
Hibernate: select count(useraddres0_.id) as col_0_0_ from user_address useraddres0_ inner join user user1_ on useraddres0_.user_id=user1_.id where (useraddres0_.address like ? escape ?) and user1_.name=? and (user1_.email like ? escape ?) and user1_.age=20
可以看到,這些查詢條件都是AND的關(guān)系。再看另外一種方法
static ExampleMatcher matchingAny() { return new TypedExampleMatcher().withMode(MatchMode.ANY); }
當(dāng)前方法與上面兩個(gè)方法不一樣的地方在于:第三個(gè)MatchMode.Any,表示查詢條件是or的關(guān)系
Hibernate: select count(useraddres0_.id) as col_0_0_ from user_address useraddres0_ inner join user user1_ on useraddres0_.user_id=user1_.id where useraddres0_.address like ? escape ? or user1_.name=? or user1_.email like ? escape ? or user1_.age=20
以上就是初始化ExampleMatcher實(shí)例的方法,你在運(yùn)用中需要注意and 和 or的關(guān)系
2、ExampleMatcher語法暴露常用方法
2.1 忽略大小寫
// 哪些屬性的paths忽略大小寫,可以指定多個(gè)參數(shù) ExampleMatcher withIgnoreCase(String... propertyPaths); // 提供一個(gè)默認(rèn)的實(shí)現(xiàn)方法,忽略大小寫 default ExampleMatcher withIgnoreCase() { return withIgnoreCase(true); } // 默認(rèn)忽略大小寫的方式,默認(rèn)false ExampleMatcher withIgnoreCase(boolean defaultIgnoreCase);
2.2 NULL值的Property的處理方式
暴露的Null值處理方式如下所示:
ExampleMatcher withNullHandler(NullHandler nullHandler);
NullHandler枚舉值如下所示:INCLUDE(包括)、IGNORE(忽略),
enum NullHandler { INCLUDE, IGNORE }
需要注意的是: 標(biāo)識(shí)作為條件的實(shí)體對(duì)象中,一個(gè)屬性值(條件值)為NULL時(shí),是否參與過濾;
當(dāng)該選項(xiàng)值是INCLUDE時(shí),標(biāo)識(shí)仍參與過濾,會(huì)匹配數(shù)據(jù)庫表中該字段值是NULL的記錄;
若為IGNORE值,表示不參與過濾;
// 把(實(shí)體類中)NULL屬性值作為查詢條件 default ExampleMatcher withIncludeNullValues() { return withNullHandler(NullHandler.INCLUDE); } // 提供一個(gè)默認(rèn)實(shí)現(xiàn)方法,忽略(實(shí)體類中)NULL屬性 default ExampleMatcher withIgnoreNullValues() { return withNullHandler(NullHandler.IGNORE); }
我們來看一下,把(實(shí)體類中)NULL屬性值作為查詢條件使用,執(zhí)行的SQL如下所示:
Hibernate: select count(useraddres0_.id) as col_0_0_ from user_address useraddres0_ inner join user user1_ on useraddres0_.user_id=user1_.id where useraddres0_.id is null or useraddres0_.address like ? escape ? or user1_.name=? or user1_.email like ? escape ? or user1_.id is null or user1_.age=20
2.3 忽略某些屬性列表,不參與查詢過濾條件
// 忽略某些屬性(可以是多個(gè)),不參與查詢過濾條件 ExampleMatcher withIgnorePaths(String... ignoredPaths);
2.4 字符串默認(rèn)的匹配規(guī)則
ExampleMatcher withStringMatcher(StringMatcher defaultStringMatcher);
默認(rèn)字符串的匹配方式有以下幾種 ,如下所示:
enum StringMatcher { DEFAULT, EXACT, STARTING, ENDING, CONTAINING, REGEX; }
DEFAULT:默認(rèn),作用和EXACT一樣
EXACT:相等
STARTING:開始匹配
ENDING:結(jié)束匹配
CONTAINING:包含、模糊匹配
REGEX:正則表達(dá)式
使用方法如下
withStringMatcher(ExampleMatcher.StringMatcher.ENDING)
或指定某些字符串屬性匹配規(guī)則
ExampleMatcher withMatcher(String propertyPath, GenericPropertyMatcher genericPropertyMatcher);
3、實(shí)踐出真理
就從上面介紹的方法,我們手動(dòng)練習(xí)一下。
新建一張Dog表
@Data @Entity @AllArgsConstructor @NoArgsConstructor @Table(name = "tb_dog") public class Dog { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(columnDefinition = "int(11) NOT NULL COMMENT '主鍵' ") private Integer id; @Column(columnDefinition = "varchar(30) DEFAULT '' COMMENT '寵物名'") private String name; @Column(columnDefinition = "int(11) DEFAULT NULL COMMENT '年齡'") private Integer age; }
3.1 AND查詢
解釋:根據(jù)當(dāng)前dog對(duì)象的屬性值作為查詢條件去查詢
@Test public void testBy01(){ Dog dog = Dog.builder() .name("TIMI") .age(2) .build(); // AND 查詢 ExampleMatcher matcher = ExampleMatcher.matching(); //ExampleMatcher.matchingAll() 也可以 System.out.println(dogRepo.findAll(Example.of(dog, matcher))); }
執(zhí)行SQL結(jié)果如下所示:
Hibernate: select dog0_.id as id1_3_, dog0_.age as age2_3_, dog0_.name as name3_3_ from tb_dog dog0_ where dog0_.name=? and dog0_.age=2
3.2 OR 查詢
解釋:根據(jù)當(dāng)前dog對(duì)象的屬性值作為查詢條件去查詢
@Test public void testBy02(){ Dog dog = Dog.builder() .name("TIMI") .age(2) .build(); // OR 查詢 ExampleMatcher matcher = ExampleMatcher.matchingAny(); System.out.println(dogRepo.findAll(Example.of(dog, matcher))); }
執(zhí)行SQL結(jié)果如下所示:
select dog0_.id as id1_3_, dog0_.age as age2_3_, dog0_.name as name3_3_ from tb_dog dog0_ where dog0_.name=? or dog0_.age=2
3.3 忽略大小寫查詢
解釋:指定"name"屬性忽略大小寫
@Test public void testBy03(){ Dog dog = Dog.builder() .name("TIMI") .age(2) .build(); ExampleMatcher matcher = ExampleMatcher.matching() .withIgnoreCase("name"); System.out.println(dogRepo.findAll(Example.of(dog, matcher))); }
執(zhí)行SQL結(jié)果如下所示:
select dog0_.id as id1_3_, dog0_.age as age2_3_, dog0_.name as name3_3_ from tb_dog dog0_ where lower(dog0_.name)=? and dog0_.age=2
在Dog表中添加type字段
@Column(columnDefinition = "varchar(20) DEFAULT NULL COMMENT '種類'") private String type;
3.3.1 忽略大小寫 不指定屬性
解釋:不指定屬性,默認(rèn)為所有查詢字符串條件加上忽略大小寫條件
@Test public void testBy04(){ Dog dog = Dog.builder() .name("TIMI") .age(2) .type("L") .build(); ExampleMatcher matcher = ExampleMatcher.matching() .withIgnoreCase(); System.out.println(dogRepo.findAll(Example.of(dog, matcher))); }
執(zhí)行SQL結(jié)果如下所示:
select dog0_.id as id1_3_, dog0_.age as age2_3_, dog0_.name as name3_3_, dog0_.type as type4_3_ from tb_dog dog0_ where lower(dog0_.name)=? and lower(dog0_.type)=? and dog0_.age=2
3.4 NULL值的處理
3.4.1 NULL屬性值作為查詢條件
解釋:把(實(shí)體類中)NULL屬性值作為查詢條件使用
@Test public void testBy05(){ Dog dog = Dog.builder() .name("TIMI") .age(2) .type("L") .build(); ExampleMatcher matcher = ExampleMatcher.matching() .withIgnoreCase() .withIncludeNullValues(); System.out.println(dogRepo.findAll(Example.of(dog, matcher))); }
執(zhí)行SQL結(jié)果如下所示:
select dog0_.id as id1_3_, dog0_.age as age2_3_, dog0_.name as name3_3_, dog0_.type as type4_3_ from tb_dog dog0_ where lower(dog0_.type)=? and (dog0_.id is null) and dog0_.age=2 and lower(dog0_.name)=?
3.4.2 忽略(實(shí)體類中)NULL屬性
解釋:把(實(shí)體類中)NULL屬性值忽略
@Test public void testBy06(){ Dog dog = Dog.builder() .name("TIMI") .age(2) .type("L") .build(); ExampleMatcher matcher = ExampleMatcher.matching() .withIgnoreNullValues(); System.out.println(dogRepo.findAll(Example.of(dog, matcher))); }
執(zhí)行SQL結(jié)果如下所示:
select dog0_.id as id1_3_, dog0_.age as age2_3_, dog0_.name as name3_3_, dog0_.type as type4_3_ from tb_dog dog0_ where dog0_.name=? and dog0_.type=? and dog0_.age=2
3.5 忽略某些屬性不做篩選
解釋:把(實(shí)體類中)某些屬性忽略掉,不做篩選
@Test public void testBy07(){ Dog dog = Dog.builder() .name("TIMI") .age(2) .type("L") .build(); // 忽略掉"name" 和 "type"兩個(gè)屬性 ExampleMatcher matcher = ExampleMatcher.matching() .withIgnorePaths("name","type"); System.out.println(dogRepo.findAll(Example.of(dog, matcher))); }
執(zhí)行SQL結(jié)果如下所示:
select dog0_.id as id1_3_, dog0_.age as age2_3_, dog0_.name as name3_3_, dog0_.type as type4_3_ from tb_dog dog0_ where dog0_.age=2
3.6 字符串匹配規(guī)則
3.6.1 DEFAULT和EXACT 相等
解釋:把(實(shí)體類中)所有字符串屬性匹配規(guī)則設(shè)置為 EXACT (相等)
@Test public void testBy08(){ Dog dog = Dog.builder() .name("TIMI") .age(2) .type("L") .build(); ExampleMatcher matcher = ExampleMatcher.matching() // 字符串屬性提供的匹配規(guī)則 EXACT相等 .withStringMatcher( ExampleMatcher.StringMatcher.EXACT); System.out.println(dogRepo.findAll(Example.of(dog, matcher))); }
執(zhí)行SQL結(jié)果如下所示:
select dog0_.id as id1_3_, dog0_.age as age2_3_, dog0_.name as name3_3_, dog0_.type as type4_3_ from tb_dog dog0_ where dog0_.name=? and dog0_.age=2 and dog0_.type=?
3.6.2 STARTING和ENDING 模糊查詢【開始匹配(?1 + %) 和 結(jié)束匹配(% + ?1 )) 】
解釋:把(實(shí)體類中)所有字符串屬性匹配規(guī)則設(shè)置為 STARTING/ENDING (模糊查詢)
public void testBy09(){ Dog dog = Dog.builder() .name("TIMI") .age(2) .type("L") .build(); ExampleMatcher matcher = ExampleMatcher.matching() // 設(shè)置為開始匹配 .withStringMatcher(ExampleMatcher.StringMatcher.STARTING); // 設(shè)置為結(jié)束匹配 //.withStringMatcher(ExampleMatcher.StringMatcher.ENDING); System.out.println(dogRepo.findAll(Example.of(dog, matcher))); }
執(zhí)行SQL結(jié)果如下所示:
select dog0_.id as id1_3_, dog0_.age as age2_3_, dog0_.name as name3_3_, dog0_.type as type4_3_ from tb_dog dog0_ where dog0_.age=2 and (dog0_.type like ? escape ?) and (dog0_.name like ? escape ?)
3.6.3 Containing 包含模糊匹配【% + ?1 + %】
解釋:把(實(shí)體類中)所有字符串屬性匹配規(guī)則設(shè)置為 Containing (包含模糊查詢)
@Test public void testBy11(){ Dog dog = Dog.builder() .name("TIMI") .age(2) .type("L") .build(); ExampleMatcher matcher = ExampleMatcher.matching() // 包含模糊查詢 .withStringMatcher(ExampleMatcher.StringMatcher.CONTAINING); System.out.println(dogRepo.findAll(Example.of(dog, matcher))); }
執(zhí)行SQL結(jié)果如下所示:
select dog0_.id as id1_3_, dog0_.age as age2_3_, dog0_.name as name3_3_, dog0_.type as type4_3_ from tb_dog dog0_ where dog0_.age=2 and (dog0_.type like ? escape ?) and (dog0_.name like ? escape ?)
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