javax.microedition.broadcast.esg
Class QueryComposer

java.lang.Object
  javax.microedition.broadcast.esg.QueryComposer

public class QueryComposer
extends java.lang.Object

QueryComposer allows database queries to be composed. There are two types of queries that can be composed:

• Simple queries are composed by specifying an attribute, a matching value and a condition.
• Compound queries are formed by combining multiple queries with some logical operators.

Here are some examples; simple queries:

 Query q1, q2, q3;
 q1 = QueryComposer.equivalent(CommonMetadataSet.SERVICE_NAME, "CNN");
 q2 = QueryComposer.currentProgram();
 q3 = QueryComposer.equivalent(CommonMetadataSet.PROGRAM_CONTENT_GENRE, StringAttribute.UNKNOWN_VALUE);
 

Compound queries:

 Query cq;
 cq = QueryComposer.and(q2, 
                QueryComposer.or(q1,
                        QueryComposer.equivalent(CommonMetadataSet.PROGRAM_CONTENT_GENRE, "News"))); 
 

The resulting queries can be used in ServiceGuide to query for matching programs, for example. On some implementations, the performance on complex compound queries can be slow.

Query rules are defined in ServiceGuide.

See Also:

ServiceGuide

Method Summary

static Query	after(DateAttribute attribute, java.util.Date value) Generate a query to test if the attribute has a time value that's after the given value.
static Query	and(Query a, Query b) Generate a compound query that's the result of taking the logical "and" of the two given queries.
static Query	before(DateAttribute attribute, java.util.Date value) Generate a query to test if the attribute has a time value that's before the given value.
static Query	contains(StringAttribute attribute, java.lang.String value) Generate a query to test if the value of a string attribute contains a given substring.
static Query	currentProgram() Generate a query to find the current broadcast programs.
static Query	equivalent(Attribute attribute, java.lang.Object value) Generate an equivalence query based on any types of attribute.
static Query	equivalent(NumericAttribute attribute, double value) Generate an equivalence query for numeric attributes.
static Query	greaterThan(NumericAttribute attribute, double value) Generate a query to test if the attribute has a value greater than the given value.
static Query	isTrue(BooleanAttribute attribute) Generate a query to test if the given attribute has a boolean value that's true.
static Query	lessThan(NumericAttribute attribute, double value) Generate a query to test if the attribute has a value less than the given value.
static Query	not(Query a) Generate a query that's the logical complement of the given query.
static Query	or(Query a, Query b) Generate a compound query that's the result of taking the logical "or" of the two given queries.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

after

public static Query after(DateAttribute attribute,
                          java.util.Date value)

Generate a query to test if the attribute has a time value that's after the given value.

Parameters:

attribute - The attribute to test against.

value - The matching value to test.

Returns:

The query object resulted. The return value must not be null.

Throws:

java.lang.NullPointerException - if any of the given arguments is null.

and

public static Query and(Query a,
                        Query b)

Generate a compound query that's the result of taking the logical "and" of the two given queries.

Parameters:

a - The first query

b - The second query

Returns:

The query object resulted. The return value must not be null.

Throws:

java.lang.NullPointerException - if any of the given arguments is null.

before

public static Query before(DateAttribute attribute,
                           java.util.Date value)

Generate a query to test if the attribute has a time value that's before the given value.

Parameters:

attribute - The attribute to test against.

value - The matching value to test.

Returns:

The query object resulted. The return value must not be null.

Throws:

java.lang.NullPointerException - if any of the given arguments is null.

contains

public static Query contains(StringAttribute attribute,
                             java.lang.String value)

Generate a query to test if the value of a string attribute contains a given substring. Test is not case sensitive.

Parameters:

attribute - The attribute to test against.

value - The substring to be tested.

Returns:

The query object resulted. The return value must not be null.

Throws:

java.lang.IllegalArgumentException - if the given String is empty.

java.lang.NullPointerException - if any of the given arguments is null.

currentProgram

public static Query currentProgram()

Generate a query to find the current broadcast programs. It is semantically equivalent to the following query Q:

 Date now = new Date();
 Query q1 = QueryComposer.before(CommonMetadataSet.PROGRAM_START_TIME, now);
 Query q1e = QueryComposer.equivalent(CommonMetadataSet.PROGRAM_START_TIME, now);
 Query q2 = QueryComposer.after(CommonMetadataSet.PROGRAM_END_TIME, now);
 Query Q = QueryComposer.and(QueryComposer.or(q1, q1e), q2);
 

Note that each time when currentProgram is called, a snapshot of the current time (i.e. new Date()) is used to form the resulted query.

equivalent

public static Query equivalent(Attribute attribute,
                               java.lang.Object value)

Generate an equivalence query based on any types of attribute. The value is given as an object. If it is a Java native type, such as an int, it will need to be wrapped with the corresponding native Java class, such as Integer in this example.

Parameters:

attribute - The attribute to test against.

value - The matching value to test.

Returns:

The query object resulted. The return value must not be null.

Throws:

java.lang.NullPointerException - if any of the given arguments is null.

java.lang.IllegalArgumentException - if


• attribute is BooleanAttribute and value is not instance of Boolean
• attribute is DateAttribute and value is not instance of Date
• attribute is NumericAttribute and value is not instance of Integer, Long, Float, Double or an instance of some other class supported by the implementation that is used to present numeric data
• attribute is StringAttribute and value is not instance of String

equivalent

public static Query equivalent(NumericAttribute attribute,
                               double value)

Generate an equivalence query for numeric attributes.

Testing equivalence for double values is precision-dependent. Two values that are closely matching may not result in an equivalence due to precision errors. Applications are advised to use a combination of greaterThan and lessThan for more controlled behavior.

Parameters:

attribute - The numeric attribute to test against.

value - The matching numeric value to test.

Returns:

The query object resulted. The return value must not be null.

Throws:

java.lang.NullPointerException - if any of the given NumericAttribute is null.

greaterThan

public static Query greaterThan(NumericAttribute attribute,
                                double value)

Generate a query to test if the attribute has a value greater than the given value.

Parameters:

attribute - The attribute to test against.

value - The matching value to test.

Returns:

The query object resulted. The return value must not be null.

Throws:

java.lang.NullPointerException - if any of the given NumericAttribute is null.

isTrue

public static Query isTrue(BooleanAttribute attribute)

Generate a query to test if the given attribute has a boolean value that's true.

Parameters:

attribute - The attribute to test against.

Returns:

The query object resulted. The return value must not be null.

Throws:

java.lang.NullPointerException - if the given argument is null.

lessThan

public static Query lessThan(NumericAttribute attribute,
                             double value)

Generate a query to test if the attribute has a value less than the given value.

Parameters:

attribute - The attribute to test against.

value - The matching value to test.

Returns:

The query object resulted. The return value must not be null.

Throws:

java.lang.NullPointerException - if any of the given NumericAttribute is null.

not

public static Query not(Query a)

Generate a query that's the logical complement of the given query.

Parameters:

a - The given query

Returns:

The query object resulted. The return value must not be null.

Throws:

java.lang.NullPointerException - if the given argument is null.

or

public static Query or(Query a,
                       Query b)

Generate a compound query that's the result of taking the logical "or" of the two given queries.

Parameters:

a - The first query

b - The second query

Returns:

The query object resulted. The return value must not be null.

Throws:

java.lang.NullPointerException - if any of the given arguments is null.