ignorecase in criteria builder in JPA

问题

How can we do a ignorecase in the criteria builder? If I have

private final CriteriaBuilder cb

then I can only use cb.asc or cb.desc, but not ignoring case.

回答1:

How can we do a ignorecase in the criteria builder

1. Force Ignorecase in JPA Program - Does the Job, Answers the Q Directly

• For a one-arg operation (i.e. ORDER BY), convert argument to lowercase (or uppercase).
• For a two-arg operation (e.g. = or LIKE or ORDER BY), convert both args to LC (or UC).

JPA ORDER BY Two Columns, Ignoring Case:

 Order lcSurnameOrder = criteriaBuilder.order(
     criteriaBuilder.lower(Person_.surname));
 Order lcFirstnameOrder = criteriaBuilder.order(
     criteriaBuilder.lower(Person_.firstname));    
 criteriaQuery.orderBy(lcSurnameOrder, lcFirstnameOrder);

JPA LIKE, Ignoring Case:

 Predicate lcSurnameLikeSearchPattern = criteriaBuilder.like(
     criteriaBuilder.lower(Person_.surname), 
     searchPattern.toLowerCase());
 criteriaQuery.where(lcSurnameLikeSearchPattern);

Assumes Person_ canonical metamodel class was generated from Person entity, to give strong-typed use of JPA criteria API.

TIP: For best performance & control, consider converting string columns to LOWER case or INITCAP case just once - when you INSERT/UPDATE into the database. Do the same conversion for user-entered search patterns.

2. ALTERNATIVE: Apply Collation in the Database - Best Practice, Simpler, More Performant

• The SQL-99 standard has a built-in modifer to compare characters in Strings according to rules:

  COLLATE <collation name>
  

  Can use when comparing, sorting and grouping on strings. A common example that ignores case:

  COLLATE SQL_Latin1_General_CP1_CI_AS
  

  Or

  COLLATE latin1_general_cs
  

  You can even create your own custom collation:

  CREATE COLLATION <collation name> FOR <character set specification>
    FROM <existing collation name> [ <pad characteristic> ]
  

• Collation is applied in the DB via one of the following alternatives (from localised to global effect):

  • WHERE Clause (=, LIKE, HAVING, >, >=, etc)

    WHERE <expression> = <expression> [COLLATE <collation name>]
    
    WHERE <expression> LIKE <expression> [COLLATE <collation name>]
    

  • SELECT DISTINCT Clause

    SELECT DISTINCT <expression> [COLLATE <collation name>], ...
    

  • ORDER BY Clause

    ORDER BY <expression> [COLLATE <collation name>]
    

  • GROUP BY Clause

    GROUP BY <expression> [COLLATE <collation name>]
    

  • Column Definition

    CREATE TABLE <table name> (
      <column name> <type name> [DEFAULT...] 
                                [NOT NULL|UNIQUE|PRIMARY KEY|REFERENCES...]
                                [COLLATE <collation name>], 
      ...
    )
    

  • Domain Definition

    CREATE DOMAIN <domain name> [ AS ] <data type>
      [ DEFAULT ... ] [ CHECK ... ] [ COLLATE <collation name> ]
    

  • Character Set Definition

    CREATE CHARACTER SET <character set name>
    [ AS ] GET <character set name> [ COLLATE <collation name> ]
    

• The first 4 cases can't be used with JPA, because these SQL commands are generated by JPA, and JPA standard does not support collation.

• The last 3 cases can be used with JPA.
• So: create TABLES with COLUMNS that have collation "turned on" and subsequently ORDER BY, =, LIKE, etc will ignore case automatically. Then no work is required in JPA - no need for any conversion or requesting to ignore case.

3. ALTERNATIVE (PROPRIETARY) Oracle also provides NLS settings to ignore case across entire DB instance (can be set in config files):

ALTER SESSION SET NLS_COMP='BINARY';    -- Case Sensitive
ALTER SESSION SET NLS_COMP='ANSI';      -- Ignore for LIKE but not =,<,etc
ALTER SESSION SET NLS_COMP='LINGUISTIC';-- Ignore for LIKE,=,<,etc (post 10gR2)

ALTER SESSION SET NLS_SORT='BINARY' ;   -- Case Sensitive
ALTER SESSION SET NLS_SORT='BINARY_CI'; -- Ignore
ALTER SESSION SET NLS_SORT='XSPANISH';  -- Ignore according to language rules
ALTER SESSION SET NLS_SORT='LATIN1_GENERAL_CS';  

Plus functions to ignore case as one-off

ORDER BY NLSSORT(supplier_name,'NLS_SORT=BINARY_CI') ;

You can call this via

criteriaBuilder.function("nlssort", String.class, dept_.suppler_name, "NLS_SORT=BINARY_CI");

and then call criteriaQuery.orderyBy or select, etc

来源：https://stackoverflow.com/questions/16611904/ignorecase-in-criteria-builder-in-jpa