处理QueryDSL中的可选参数

时间：2014-05-20 03:24:05

标签： java spring-data querydsl

我在SpringData中使用QueryDSL。 我有表说，Employee我创建了实体类，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Spring数据将 QueryDSL 用于 QueryDSL 中的可选参数？

谢谢：）

9 个答案:

答案 0 :(得分：29)

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);
}

答案 1 :(得分：8)

BooleanBuilder很好。您也可以将其包装并添加＆＃34;可选＆＃34;方法，以避免if条件：

例如，对于＆＃34;和＆＃34;你可以写:(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();
    }

然后使用会更清洁：

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

答案 2 :(得分：3)

实际上这是Java 101：检查null并初始化查询而不是连接谓词。所以像这样的辅助方法可以解决这个问题：

private BooleanExpression createOrAnd(BooleanExpression left, BooleanExpression right) {
  return left == null ? right : left.and(right);
}

然后你就可以做到：

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，我甚至在第一个子句中使用createOrAnd(…)只是为了保持一致性，并且如果您决定在firstName之前添加新子句，则不必调整该代码。< / p>

答案 3 :(得分：1)

我遇到了同样的问题，下面是使用for /R "C:\extract" %%I in ("*.7z_encrpt") do ("C:\Program Files\7-Zip\7z.exe" X -y -o"%%~dpI" "%%~fI") for /R "C:\extract" %%I in ("*.zip_encrpt") do ("C:\Program Files\7-Zip\7z.exe" X -y -o"%%~dpI" "%%~fI") 的{​​{3}}的Timo Westkämper 的另一个版本。

Optional

答案 4 :(得分：0)

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。

答案 5 :(得分：0)

根据你的需要我会做到这一点

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List EmployeeEntity。其次，使用可选项比检查其null更好，并且您可以传递从可选的Optional获得的Java 8 RequestParam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";
  }
}

查看here。

答案 6 :(得分：0)

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();
}

答案 7 :(得分：0)

还有一种使用Optional而不使用BooleanBuilder的方法，尽管结果查询可能有点冗长：

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);
}

采用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);
}

答案 8 :(得分：0)

对于任何想要基于动态请求参数映射而非特定参数构建谓词的人，都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);
    }
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