QueryDSL Dynamic Predicates

Question

I need help with querying QueryDSL. I use this library with Spring Data JPA. My class of service:

@Service("tblActivityService")
public class TblActivityService implements AbstractService<TblActivity> {

@Resource
private TblActivityRepository tblActivityRepository;

@Override
public List<TblActivity> findAll(Predicate predicate) {
    return (List<TblActivity>) tblActivityRepository.findAll(predicate);
}
}

I have a dynamic filter list:

@Entity
@Table(name = "sys_filters")
public class SysFilter implements Serializable {
private static final long serialVersionUID = 1L;

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Basic(optional = false)
@Column(name = "filter_id")
private Integer filterId;

@JoinColumn(name = "user_id", referencedColumnName = "user_id")
@ManyToOne(fetch = FetchType.EAGER)
private SysUser userId;

@Size(max = 45)
@Column(name = "table_name")
private String tableName;

@Size(max = 45)
@Column(name = "column_name")
private String columnName;

@Size(max = 45)
@Column(name = "condition")
private String condition;

@Size(max = 100)
@Column(name = "value")
private String value;


// getters & setters

}

I have a column name (e.g. name) I have a condition (e.g. == ,! =,> = Etc.) - I can store it as characters or words (equal, etc.), AND finally i have value.

The question is how to dynamically generate a predicate for my service? The table contains about 25 fields.

The predicate looks like this:

public BooleanExpression buildFilteredResult(List<SysFilter> filters) {
    //TODO do it!
    return QTblActivity.tblActivity.title.eq("Value"); 
// I need to do it dynamically for each filter in the list
}

The problem is how to call columnName by its string value. Do you have any suggestions?

Answer 1

Map<String, Operator> operators = ImmutableMap.of(
  "==", Ops.EQ, "!=", Ops.NE, ">", Ops.GT, "<", Ops.LT,
  ">=", Ops.GOE, "<=", Ops.LOE);

Expressions.predicate(operators.get(condition), 
  stringPath, Expressions.constant(filterValue));

,

predicates.and(...)

predicates .

, BooleanBuilder - , ?

Answer 2

:

public BooleanExpression buildFilteredResult(List<SysFilter> filters) {
    //TODO do it!

    QTblActivity qTblActivity = QTblActivity.tblActivity;
    BooleanExpression expression = qTblActivity.recordState;

    for (SysFilter filter : filters) {
        StringPath stringPath = new StringPath(qTblActivity, filter.getColumnName());
        switch (filter.getCondition()) {
            case "==":
                expression.and(stringPath.eq(filter.getValue()));
                break;
            case "!=":
                expression.and(stringPath.ne(filter.getValue()));
                break;
            case ">":
                expression.and(stringPath.gt(filter.getValue()));
                break;
            case "<":
                expression.and(stringPath.lt(filter.getValue()));
                break;
            case ">=":
                expression.and(stringPath.goe(filter.getValue()));
                break;
            case "<=":
                expression.and(stringPath.loe(filter.getValue()));
                break;
            default:
                break;
        }
    }

    return expression;

}

Answer 3

spring /. -, - querydsl, , - get , - - (, ...), . .