在QueryDSL中處理可選參數

我對SpringData使用QueryDSL。我有表說，Employee和我已經創建實體類說，EmployeeEntity 我已經寫以下服務方法在QueryDSL中處理可選參數

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); 
}

如上我評論的NPException。如何使用QueryDSL獲取可選參數QueryDSL使用Spring Data？

謝謝:)

來源

2014-05-20 Prashant Shilimkar

BooleanBuilder可以用作布爾表達式動態生成器：

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); 
}

來源

2014-05-27 18:17:42

但如果我們加入？你能幫我嗎？http://stackoverflow.com/questions/24792778/dynamic-search-by-criteria – Youssef

這是Java的101實際上是：檢查null和初始化查詢，而不是串聯的謂詞。所以像這樣的helper方法可以做的伎倆：

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

然後，你可以簡單地做：

BooleanExpression query = null; 

if (firstName != null) { 
    query = createOrAnd(query, employee.firstName.eq(firstName)); 
} 

if (lastName != null) { 
    query = createOrAnd(query, employee.lastName.eq(lastName)); 
} 

…

請注意，我用createOrAnd(…)即使是在第一條簡單的一致性，並沒有如果您決定在firstName之前添加新條款，請修改該代碼。

來源

2014-05-20 07:03:20

你救了我的時間:) –

如果選中QueryDSL實施null：

public BooleanExpression and(@Nullable Predicate right) { 
    right = (Predicate) ExpressionUtils.extract(right); 
    if (right != null) { 
     return BooleanOperation.create(Ops.AND, mixin, right); 
    } else { 
     return this; 
    } 
}

按理說它是你想要的。

來源

2014-05-25 20:15:39 ameen

此基礎上，你需要，我會做到這一點

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); 
}

，首先你應該返回EmployeeEntity的List什麼。其次，它能夠更好地使用可選的比，如果其null檢查，你可以通過從Java可選RequestParam的像這樣獲得8的Optional值：

@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);  
      .... 
}

而且很重要的是要使用containsIgnoreCase功能謂語：比典型的like更好導致其不區分大小寫。

在我看來，你應該使用一些方法是這樣的：

@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"; 
    } 
}

看看它在here。

來源

2015-09-25 15:54:05 EliuX

BooleanBuilder很好。你也可以把它包起來，爲了避免如果添加條件「可選」的方法：

例如，對於「和」你可以這樣寫：（Java的8個lambda表達式中使用）

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(); 
    }

然後使用會更清潔：

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)) 
    ); 
}

很可能也使用JDK的可選類

來源

2015-11-02 15:20:14 aviad

在QueryDSL中處理可選參數

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