在Spring中使用RSQL实现REST查询语言
REST API提供一种搜索/查询语言能够类似SQL那样实现REST API的干净简单且强大的操作。rsql-parser是一个提供REST查询语言RSQL的强大库包。RSQL是Feed Item Query Language (简称:FIQL)的子集。
下面我们看看在Spring中实现RSQL的大概步骤:
首先,我们导入RSQL Maven包:
<dependency>
<groupId>cz.jirutka.rsql</groupId>
<artifactId>rsql-parser</artifactId>
<version>2.0.0</version>
</dependency>
定义主要业务领域模型实体如下:
@Entity
public class User {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String firstName;
private String lastName;
private String email;
private int age;
}
下面我们开始解析REST客户端的请求:
RSQL表达式内部以节点形式表达,所以,这里一般使用访问者模式作实现输入分析,必须记住,我们需要实现接口 RSQLVisitor interface, 并且创建我们自己的访问者实现 – CustomRsqlVisitor:
public class CustompRsqlVisitor<T> implements RSQLVisitor<Specification<User>, Void> {
private UserRsqlSpecBuilder builder;
public CustomRsqlVisitor() {
builder = new UserRsqlSpecBuilder();
}
@Override
public Specification<User> visit(AndNode node, Void param) {
return builder.createSpecification(node);
}
@Override
public Specification<User> visit(OrNode node, Void param) {
return builder.createSpecification(node);
}
@Override
public Specification<User> visit(ComparisonNode node, Void params) {
return builder.createSecification(node);
}
}
现在我们需要处理持久层,为这些每个节点构造查询。这里使用Spring Data JPA规格,实现一个规格构建器,用来构建我们要访问的每个节点的规格。
public class UserRsqlSpecBuilder {
public Specifications<User> createSpecification(Node node) {
if (node instanceof LogicalNode) {
return createSpecification((LogicalNode) node);
}
if (node instanceof ComparisonNode) {
return createSpecification((ComparisonNode) node);
}
return null;
}
public Specifications<User> createSpecification(LogicalNode logicalNode) {
List<Specifications<User>> specs = new ArrayList<Specifications<User>>();
Specifications<User> temp;
for (Node node : logicalNode.getChildren()) {
temp = createSpecification(node);
if (temp != null) {
specs.add(temp);
}
}
Specifications<User> result = specs.get(0);
if (logicalNode.getOperator() == LogicalOperator.AND) {
for (int i = 1; i < specs.size(); i++) {
result = Specifications.where(result).and(specs.get(i));
}
} else if (logicalNode.getOperator() == LogicalOperator.OR) {
for (int i = 1; i < specs.size(); i++) {
result = Specifications.where(result).or(specs.get(i));
}
}
return result;
}
public Specifications<User> createSpecification(ComparisonNode comparisonNode) {
Specifications<User> result = Specifications.where(
new UserRsqlSpecification(
comparisonNode.getSelector(),
comparisonNode.getOperator(),
comparisonNode.getArguments()
)
);
return result;
}
}
注意:
- LogicalNode是AND/OR节点,有多个子节点
- ComparisonNode 则是没有子节点,它保留有 Selector, Operator 和 参数Arguments
举例,对于查询“name==john” – 可得:
- Selector则是: “name”
- Operator则是: “==”
- Arguments则是:[john]
下面我们创建一个定制的规格:当构建查询时,我们需要利用一个定制的User Specification – “UserRsqlSpecification“:
public class UserRsqlSpecification implements Specification<User> {
private String property;
private ComparisonOperator operator;
private List<String> arguments;
public UserRsqlSpecification(
String property, ComparisonOperator operator, List<String> arguments) {
super();
this.property = property;
this.operator = operator;
this.arguments = arguments;
}
@Override
public Predicate toPredicate(
Root<User> root, CriteriaQuery<?> query, CriteriaBuilder builder) {
List<Object> args = castArguments(root);
Object argument = args.get(0);
switch (RsqlSearchOperation.getSimpleOperator(operator)) {
case EQUAL: {
if (argument instanceof String) {
return builder.like(
root.<String> get(property), argument.toString().replace('*', '%'));
} else if (argument == null) {
return builder.isNull(root.get(property));
} else {
return builder.equal(root.get(property), argument);
}
}
case NOT_EQUAL: {
if (argument instanceof String) {
return builder.notLike(
root.<String> get(property), argument.toString().replace('*', '%'));
} else if (argument == null) {
return builder.isNotNull(root.get(property));
} else {
return builder.notEqual(root.get(property), argument);
}
}
case GREATER_THAN: {
return builder.greaterThan(root.<String> get(property), argument.toString());
}
case GREATER_THAN_OR_EQUAL: {
return builder.greaterThanOrEqualTo(
root.<String> get(property), argument.toString());
}
case LESS_THAN: {
return builder.lessThan(root.<String> get(property), argument.toString());
}
case LESS_THAN_OR_EQUAL: {
return builder.lessThanOrEqualTo(
root.<String> get(property), argument.toString());
}
case IN:
return root.get(property).in(args);
case NOT_IN:
return builder.not(root.get(property).in(args));
}
return null;
}
private List<Object> castArguments(Root<User> root) {
List<Object> args = new ArrayList<Object>();
Class<? extends Object> type = root.get(property).getJavaType();
for (String argument : arguments) {
if (type.equals(Integer.class)) {
args.add(Integer.parseInt(argument));
} else if (type.equals(Long.class)) {
args.add(Long.parseLong(argument));
} else {
args.add(argument);
}
}
return args;
}
}
下面是枚举enum “RsqlSearchOperation“ ,其保留有默认的rsql-parser operator:
public enum RsqlSearchOperation {
EQUAL(RSQLOperators.EQUAL),
NOT_EQUAL(RSQLOperators.NOT_EQUAL),
GREATER_THAN(RSQLOperators.GREATER_THAN),
GREATER_THAN_OR_EQUAL(RSQLOperators.GREATER_THAN_OR_EQUAL),
LESS_THAN(RSQLOperators.LESS_THAN),
LESS_THAN_OR_EQUAL(RSQLOperators.LESS_THAN_OR_EQUAL),
IN(RSQLOperators.IN),
NOT_IN(RSQLOperators.NOT_IN);
private ComparisonOperator operator;
private RsqlSearchOperation(ComparisonOperator operator) {
this.operator = operator;
}
public static RsqlSearchOperation getSimpleOperator(ComparisonOperator operator) {
for (RsqlSearchOperation operation : values()) {
if (operation.getOperator() == operator) {
return operation;
}
}
return null;
}
}
好了,REST 查询语言核心功能基本开发完毕,下面我们来测试一下:
首先,初始化一下数据:
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = { PersistenceConfig.class })
@Transactional
@TransactionConfiguration
public class RsqlTest {
@Autowired
private UserRepository repository;
private User userJohn;
private User userTom;
@Before
public void init() {
userJohn = new User();
userJohn.setFirstName("john");
userJohn.setLastName("doe");
userJohn.setEmail("john@doe.com");
userJohn.setAge(22);
repository.save(userJohn);
userTom = new User();
userTom.setFirstName("tom");
userTom.setLastName("doe");
userTom.setEmail("tom@doe.com");
userTom.setAge(26);
repository.save(userTom);
}
}
测试操作符operator是等于号”=“的查询:
查询所有姓是john和名是doe的所有用户
@Test
public void givenFirstAndLastName_whenGettingListOfUsers_thenCorrect() {
Node rootNode = new RSQLParser().parse("firstName==john;lastName==doe");
Specification<User> spec = rootNode.accept(new CustomRsqlVisitor<User>());
List<User> results = repository.findAll(spec);
assertThat(userJohn, isIn(results));
assertThat(userTom, not(isIn(results)));
}
测试“不等于"的查询:
查询姓不是"john"的所有用户
@Test
public void givenFirstNameInverse_whenGettingListOfUsers_thenCorrect() {
Node rootNode = new RSQLParser().parse("firstName!=john");
Specification<User> spec = rootNode.accept(new CustomRsqlVisitor<User>());
List<User> results = repository.findAll(spec);
assertThat(userTom, isIn(results));
assertThat(userJohn, not(isIn(results)));
}
测试“大于>”的查询:
查询年龄大于25的用户
@Test
public void givenMinAge_whenGettingListOfUsers_thenCorrect() {
Node rootNode = new RSQLParser().parse("age>25");
Specification<User> spec = rootNode.accept(new CustomRsqlVisitor<User>());
List<User> results = repository.findAll(spec);
assertThat(userTom, isIn(results));
assertThat(userJohn, not(isIn(results)));
}
测试"Like"查询
查询姓中有字符"jo"的用户
@Test
public void givenFirstNamePrefix_whenGettingListOfUsers_thenCorrect() {
Node rootNode = new RSQLParser().parse("firstName==jo*");
Specification<User> spec = rootNode.accept(new CustomRsqlVisitor<User>());
List<User> results = repository.findAll(spec);
assertThat(userJohn, isIn(results));
assertThat(userTom, not(isIn(results)));
}
测试IN:查询姓中是 “john” 或 “jack“的用户:
@Test
public void givenListOfFirstName_whenGettingListOfUsers_thenCorrect() {
Node rootNode = new RSQLParser().parse("firstName=in=(john,jack)");
Specification<User> spec = rootNode.accept(new CustomRsqlVisitor<User>());
List<User> results = repository.findAll(spec);
assertThat(userJohn, isIn(results));
assertThat(userTom, not(isIn(results)));
}
最后一步,将所有的功能放入控制器:
@RequestMapping(method = RequestMethod.GET, value = "/users")
@ResponseBody
public List<User> findAllByRsql(@RequestParam(value = "search") String search) {
Node rootNode = new RSQLParser().parse(search);
Specification<User> spec = rootNode.accept(new CustomRsqlVisitor<User>());
return dao.findAll(spec);
}
通过浏览器访问:
http://localhost:8080/users?search=firstName==jo*;age<25
得到结果是:
[{
"id":1,
"firstName":"john",
"lastName":"doe",
"email":"john@doe.com",
"age":24
}]
完整源码见:the github project
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