[英]Handle optional parameters in QueryDSL
我在 SpringData 中使用 QueryDSL。 我有表说, Employee
和我创建了实体类说, EmployeeEntity
我写了以下服务方法
public EmployeeEntity getEmployees(String firstName, String lastName)
{
QEmployeeEntity employee = QEmployeeEntity.employeeEntity;
BooleanExpression query = null;
if(firstName != null)
{
query = employee.firstName.eq(firstName);
}
if(lastName != null)
{
query = query.and(employee.lastName.eq(lastName)); // NPException if firstName is null as query will be NULL
}
return empployeeDAO.findAll(query);
}
如上所述,我评论了NPException
。 如何使用QueryDSL为使用Spring数据在QueryDSL可选参数?
谢谢 :)
BooleanBuilder
可以用作布尔表达式的动态构建器:
public EmployeeEntity getEmployees(String firstName, String lastName) {
QEmployeeEntity employee = QEmployeeEntity.employeeEntity;
BooleanBuilder where = new BooleanBuilder();
if (firstName != null) {
where.and(employee.firstName.eq(firstName));
}
if (lastName != null) {
where.and(employee.lastName.eq(lastName));
}
return empployeeDAO.findAll(where);
}
BooleanBuilder 很好。 您还可以包装它并添加“可选”方法以避免 if 条件:
例如,对于“and”,您可以编写:(使用 Java 8 lambdas)
public class WhereClauseBuilder implements Predicate, Cloneable
{
private BooleanBuilder delegate;
public WhereClauseBuilder()
{
this.delegate = new BooleanBuilder();
}
public WhereClauseBuilder(Predicate pPredicate)
{
this.delegate = new BooleanBuilder(pPredicate);
}
public WhereClauseBuilder and(Predicate right)
{
return new WhereClauseBuilder(delegate.and(right));
}
public <V> WhereClauseBuilder optionalAnd(@Nullable V pValue, LazyBooleanExpression pBooleanExpression)
{
return applyIfNotNull(pValue, this::and, pBooleanExpression);
}
private <V> WhereClauseBuilder applyIfNotNull(@Nullable V pValue, Function<Predicate, WhereClauseBuilder> pFunction, LazyBooleanExpression pBooleanExpression)
{
if (pValue != null)
{
return new WhereClauseBuilder(pFunction.apply(pBooleanExpression.get()));
}
return this;
}
}
@FunctionalInterface
public interface LazyBooleanExpression
{
BooleanExpression get();
}
然后使用会更干净:
public EmployeeEntity getEmployees(String firstName, String lastName) {
QEmployeeEntity employee = QEmployeeEntity.employeeEntity;
return empployeeDAO.findAll
(
new WhereClauseBuilder()
.optionalAnd(firstName, () -> employee.firstName.eq(firstName))
.optionalAnd(lastName, () -> employee.lastName.eq(lastName))
);
}
也可以使用 jdk 的 Optional 类
这实际上是 Java 101:检查null
并初始化查询而不是连接谓词。 因此,像这样的辅助方法可以解决问题:
private BooleanExpression createOrAnd(BooleanExpression left, BooleanExpression right) {
return left == null ? right : left.and(right);
}
然后你可以简单地做:
BooleanExpression query = null;
if (firstName != null) {
query = createOrAnd(query, employee.firstName.eq(firstName));
}
if (lastName != null) {
query = createOrAnd(query, employee.lastName.eq(lastName));
}
…
请注意,我什至在第一createOrAnd(…)
使用createOrAnd(…)
只是为了保持一致性,并且如果您决定在firstName
子句之前添加一个新子句,则不必修改该代码。
如果您检查null
的 QueryDSL 实现:
public BooleanExpression and(@Nullable Predicate right) {
right = (Predicate) ExpressionUtils.extract(right);
if (right != null) {
return BooleanOperation.create(Ops.AND, mixin, right);
} else {
return this;
}
}
这应该是你想要的。
我遇到了同样的问题,这里是Timo Westkämper使用Optional
接受的答案的另一个版本。
default Optional<Correlation> findOne(
@Nonnull final String value, @Nullable final String environment,
@Nullable final String application, @Nullable final String service) {
final QSome Some = QSome.some;
final BooleanBuilder builder = new BooleanBuilder();
ofNullable(service).map(some.service::eq).map(builder::and);
ofNullable(application).map(some.application::eq).map(builder::and);
ofNullable(environment).map(some.environment::eq).map(builder::and);
builder.and(some.value.eq(value));
return findOne(builder);
}
对于任何想要基于动态请求参数映射而不是特定的谓词构建谓词的人,可以使用以下简单格式,
public List<User> searchUser(Map<String, Optional<String>> requestParams ){
QUser qUser = Quser.qUser;
BooleanBuilder builder = new BooleanBuilder();
requestParams.forEach( (String key, String value) -> {
if(!value.isEmpty()) {
StringPath column = Expressions.stringPath(qUser, key);
builder.and(column.eq(value));
}
});
}
这是我的控制器
@RequestMapping(value = "", method = RequestMethod.GET)
public ResponseEntity<List<User>> searchUser(
@RequestParam() Map<String, Optional<String>> requestParams) {
List<User> userList = userService.searchUser(requestParams);
if(userList!=null)
return new ResponseEntity<>(userList, HttpStatus.OK);
else
return new ResponseEntity<>(userList, HttpStatus.INTERNAL_SERVER_ERROR);
}
根据您的需要,我会这样做
public List<EmployeeEntity> getEmployees(Optional<String> firstName, Optional<String> lastName)
{
BooleanExpression queryPredicate = QEmployeeEntity.employeeEntity.firstName.containsIgnoreCase(firstName.orElse("")).and(QEmployeeEntity.employeeEntity.lastName.containsIgnoreCase(lastName.orElse("")));
return empployeeDAO.findAll(queryPredicate);
}
首先,您应该返回一个EmployeeEntity
List
。 其次,使用 optional 比检查它是否为null
更好,您可以传递从可选RequestParam
获得的 Java 8 Optional
值,如下所示:
@RequestMapping(value = "/query", method = RequestMethod.GET)
public ModelAndView queryEmployee(@RequestParam(value = "firstName", required = false) Optional<String> firstName, @RequestParam(value = "lastName", required = false) Optional<String> lastName)
{
List<EmployeeEntity> result = getEmployees(firstName, lastName);
....
}
一个非常重要的事情是在谓词中使用containsIgnoreCase
函数:它比典型的like
更好,因为它不区分大小写。
在我看来,你应该使用这样的方法:
@Controller
class UserController {
@Autowired UserRepository repository;
@RequestMapping(value = "/", method = RequestMethod.GET)
String index(Model model, @QuerydslPredicate(root = User.class) Predicate predicate,
Pageable pageable, @RequestParam MultiValueMap<String, String> parameters) {
model.addAttribute("users", repository.findAll(predicate, pageable));
return "index";
}
}
看看这里。
这是处理可选参数的一种非常简单的方法,我在我的项目中使用它:
public List<ResultEntity> findByOptionalsParams(String param1, Integer param2) {
QResultEntity qResultEntity = QResultEntity.resultEntity;
final JPQLQuery<ResultEntity> query = from(qResultEntity);
if (!StringUtils.isEmpty(param1)) {
query.where(qResultEntity.field1.like(Expressions.asString("%").concat(param1).concat("%")));
}
if (param2 != null) {
query.where(qResultEntity.field2.eq(param2));
}
return query.fetch();
}
尽管结果查询可能有点冗长,但还有另一种使用Optional
而不使用BooleanBuilder
方法:
public EmployeeEntity getEmployees(String firstName, String lastName) {
QEmployeeEntity employee = QEmployeeEntity.employeeEntity;
BooleanExpression where = ofNullable(firstName).map(employee.firstName::eq).orElse(Expressions.TRUE)
.and(ofNullable(lastName).map(employee.lastName::eq).orElse(Expressions.TRUE));
return empployeeDAO.findAll(where);
}
考虑到这个想法并添加一个辅助函数可以提高可读性:
public EmployeeEntity getEmployees(String firstName, String lastName) {
QEmployeeEntity employee = QEmployeeEntity.employeeEntity;
BooleanExpression where = optionalExpression(firstName, employee.firstName::eq)
.and(optionalExpression(lastName, employee.lastName::eq));
return empployeeDAO.findAll(where);
}
public static <T> BooleanExpression optionalExpression(T arg, Function<T, BooleanExpression> expressionFunction) {
if (arg == null) {
return Expressions.TRUE;
}
return expressionFunction.apply(arg);
}
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