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com.tangosol.util
Class QueryHelper

java.lang.Object
com.tangosol.util.QueryHelper

public class QueryHelper

extends java.lang.Object

QueryHelper is a utility class that provides a set of factory methods used for building instances of Filter or ValueExtractor.

The QueryHelper API accepts a String that specifies the creation of rich Filters in a format similar to SQL WHERE clauses. For example, the String "street = 'Main' and state = 'TX'" will create a tree of Filters similar to the following Java code:

new AndFilter(
new EqualsFilter("getStreet","Main"),
new EqualsFilter("getState","TX"));


The following keywords are currently supported (words between brackets are optional):

• Comparison operators: =, >, >=, <, <=, <>, [ NOT ] BETWEEN, [ NOT ] LIKE, [ NOT ] IN, IS [ NOT ] NULL , CONTAINS [ ALL | ANY ]
• Logical operators: (AND, OR, NOT)
• Literal numbers, and the constants true, false, and null

Each argument to an operator is converted into a ReflectionExtractor. Additionally, the "." operator will use ChainedExtractor. Pseudo functions key() and value() may be used to specify the use of a key as in "key() between 10 and 50". The value() pseudo function is a shorthand for IdentityExtractor.

Query bind variables are supported in two forms. One form is a "?" followed by a position number; for example: "dept = ?1 and serviceCode in [10,20,30]". For this usage, supply an Object array of parameters to createFilter(String, Object[]). Note: this scheme treats 1 as the starting index into the array.

Additionally, named bind parameters are supported. The above example could be: "dept = :deptNum and serviceCode in :myList". This style requires the use of a Map with createFilter(String, Map). Both forms can be used in the same specification.

The factory methods catch a number of Exceptions from the implementation stages and subsequently may throw an unchecked FilterBuildingException.

Author:

djl 2009.9.3

Constructor Summary

QueryHelper()

Method Summary

static ValueExtractor	createExtractor(java.lang.String s) Make a new ValueExtractor from the given String.
static Filter	createFilter(java.lang.String s) Make a new Filter from the given String.
static Filter	createFilter(java.lang.String s, java.util.Map mapBindings) Make a new Filter from the given String.
static Filter	createFilter(java.lang.String s, java.lang.Object[] aBindings) Make a new Filter from the given String.
static Filter	createFilter(java.lang.String s, java.lang.Object[] aBindings, java.util.Map mapBindings) Make a new Filter from the given String.
static java.lang.Object	executeStatement(java.lang.String sStatement) Execute a CohQL statement.

Constructor Detail

QueryHelper

public QueryHelper()

Method Detail

createFilter

public static Filter createFilter(java.lang.String s)

Make a new Filter from the given String.

Parameters:

s - a String in the Coherence Query Language representing a Filter

Returns:

the constructed Filter

Throws:

FilterBuildingException - may be thrown

createFilter

public static Filter createFilter(java.lang.String s,
                                  java.lang.Object[] aBindings)

Make a new Filter from the given String.

Parameters:

s - a String in the Coherence Query Language representing a Filter

aBindings - the array of Objects to use for Bind vars

Returns:

the constructed Filter

Throws:

FilterBuildingException - may be thrown

createFilter

public static Filter createFilter(java.lang.String s,
                                  java.util.Map mapBindings)

Make a new Filter from the given String.

Parameters:

s - a String in the Coherence Query Language representing a Filter

mapBindings - the Map of Objects to use for Bind vars

Returns:

the constructed Filter

Throws:

FilterBuildingException - may be thrown

createFilter

public static Filter createFilter(java.lang.String s,
                                  java.lang.Object[] aBindings,
                                  java.util.Map mapBindings)

Make a new Filter from the given String.

Parameters:

s - a String in the Coherence Query Language representing a Filter

aBindings - the array of Objects to use for Bind vars

mapBindings - the Map of Objects to use for Bind vars

Returns:

the constructed Filter

Throws:

FilterBuildingException - may be thrown

createExtractor

public static ValueExtractor createExtractor(java.lang.String s)

Make a new ValueExtractor from the given String.

Parameters:

s - a String in the Coherence Query Language representing a ValueExtractor

Returns:

the constructed ValueExtractor

Throws:

FilterBuildingException - may be thrown

executeStatement

public static java.lang.Object executeStatement(java.lang.String sStatement)

Execute a CohQL statement. This method accepts a complete query string as the argument. The type of object returned depends on the query:

Return Type	Query Description
Cache entry value	If the statement is an INSERT operation the previous entry for the given key will be returned; otherwise null
Number	If the query is an aggregation that returns a single numerical value; for example: count(), avg(), max(), min()
Map	If query has a grouping
Collection	For all other SELECT, DELETE, UPDATE statements
null	If the query returns no results or for create/delete index or drop/create cache, or backup/restore

Parameters:

sStatement - a Coherence Query Language statement

Returns:

the query results

Throws:

java.lang.RuntimeException - if an invalid query is provided

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