class QueryObject {
private Class klass;
private List criteria = new ArrayList();
public Set execute(UnitOfWork uow) {
this.uow = uow;
return uow.getMapper(klass).findObjectsWhere(generateWhereClause());
}
private String generateWhereClause() {
StringBuffer result = new StringBuffer();
for (Iterator it = criteria.iterator(); it.hasNext();) {
Criteria c = (Criteria)it.next();
if (result.length()!= 0)
result.append("AND");
result.append(c.generateSql(uow.getMapper(klass).getDataMap));
}
return result.toString();
}
}
class Criteria {
private String sqlOperator;
protected String field;
protected Object value;
public static Criteria greaterThan(String fieldName, int value) {
return Criteria.greaterThan(fieldName, new Integer(value));
}
public static Criteria greaterThan(String fieldName, Object value) {
return new Criteria(" > ", fieldName, value);
}
private Criteria(String sql, String field, Object value) {
this.sqlOperator = sql;
this.field = field;
this.value = value;
}
public String generateSql(DataMap dataMap) {
return dataMap.getColumnForField(field) + sqlOperator + value;
}
public static Criteria matches(String fieldName, String pattern){
return new MatchCriteria(fieldName, pattern);
}
}
public class Person{
private String lastName;
private String firstName;
private int numberOfDependents
}
class MatchCriteria extends Criteria{
public String generateSql(DataMap dataMap) {
return "UPPER(" + dataMap.getColumnForField(field) + ") LIKE UPPER('" + value + "')";
}
}
class Mapper {
public Set findObjectsWhere (String whereClause) {
String sql = "SELECT" + dataMap.columnList() + " FROM " + dataMap.getTableName() + " WHERE "
+ whereClause;
PreparedStatement stmt = null;
ResultSet rs = null;
Set result = new HashSet();
try {
stmt = DB.prepare(sql);
rs = stmt.executeQuery();
result = loadAll(rs);
} catch (Exception e) {
throw new ApplicationException (e);
} finally {DB.cleanUp(stmt, rs);
}
return result;
}
}
class DataMap {
public String getColumnForField (String fieldName) {
for (Iterator it = getColumns(); it.hasNext();) {
ColumnMap columnMap = (ColumnMap)it.next();
if (columnMap.getFieldName().equals(fieldName))
return columnMap.getColumnName();
}
throw new ApplicationException ("Unable to find column for " + fieldName);
}
}
public class Client{
public static void main(String []args){
QueryObject query = new QueryObject(Person.class);
query.addCriteria(Criteria.greaterThan("numberOfDependents", 0));
UnitOfWork uow = new UnitOfWork();
query.execute(uow);
}
}
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