查询定义 除了数据定义，实现搜索API还需要查询定义。我们已经创建了一组类，用来实现亚马逊的查询定义。 这个搜索查询的核心是过滤器。我们引入了SearchQueryFilter 接口，并提供了两种实现方式——Search Query Value Filter（列表3）和Search Query Filter Operation（列表4）。 public class SearchQueryValueFilter implements SearchQueryFilter{
private String _field;
private String _value;
private boolean _isExclude;
private boolean _isNumeric;
public SearchQueryValueFilter(){}
public SearchQueryValueFilter(String field, String value, boolean isNumeric, boolean isExclude){
_field = field;
_value = value;
_isExclude = isExclude;
_isNumeric = isNumeric;
}
public String getField() {
return _field;
}
public void setField(String field) {
_field = field;
}
public String getValue() {
return _value;
}
public void setValue(String value) {
_value = value;
}
public boolean isExclude() {
return _isExclude;
}
public void setExclude(boolean isExclude) {
_isExclude = isExclude;
}
public boolean isNumeric() {
return _isNumeric;
}
public void setNumeric(boolean isNumeric) {
_isNumeric = isNumeric;
}
@Override
public String toString(){
StringBuffer sb = new StringBuffer();
if(_isExclude){
sb.append("(not ");
}
if(_field != null){
sb.append(_field);
sb.append(":");
}
if(!_isNumeric){
sb.append("'");
}
sb.append(_value);
if(!_isNumeric){
sb.append("'");
}
if(_isExclude){
sb.append(")");
}
return sb.toString();
}
}
Listing 3 Value filter implementation
public class SearchQueryFilterOperation implements SearchQueryFilter {
List<SearchQueryFilter> _filters;
FilterOperation _operation;
public SearchQueryFilterOperation(){
_operation = FilterOperation.and;
_filters = new LinkedList<SearchQueryFilter>();
}
public List<SearchQueryFilter> getFilters() {
return _filters;
}
public void setFilters(List<SearchQueryFilter> filters) {
_filters = filters;
}
public void addFilters(SearchQueryFilter filter) {
_filters.add(filter);
}
public FilterOperation getOperation() {
return _operation;
}
public void setOperation(FilterOperation operation) {
_operation = operation;
}
@Override
public String toString() {
StringBuffer sb = new StringBuffer();
sb.append("(");
sb.append(_operation);
for(SearchQueryFilter f : _filters){
sb.append(" ");
sb.append(f);
}
sb.append(")");
return sb.toString();
}
public enum FilterOperation{
and, or
}
}
Listing 4 Operation filter implementation
Search Query Value Filter类支持开发者使用等于、小于、大于、区间（同样支持负值比较）等运算符设置单个字段的限制。而Search Query Filter Operation类还支持开发者使用AND/OR操作符，将多个Search Query Value Filters和Search Query Filter Operations组合使用。通过这两个类的组合使用，就能实现亚马逊云搜索所支持的任意查询过滤器的表达式了。 亚马逊云搜索支持分面分类（Faceted classification）：
分面分类应用于分面搜索系统，用户在这种系统中能够从多方面进行信息的导航（译者注：如书籍可以从作者、主题、出版日期等不同的分面），多方面对应于不同顺序的分面。 AWS支持按分面控制搜索执行以及对搜索结果排序。同时还支持开发者控制返回的搜索结果中包含的分面数量。所有的分面操作由Search Query Facet（列表5）这个类来实现。 public class SearchQueryFacet {
private String _name;
private int _maxFacets;
private List<String> _constraints;
private FacetSort _sort;
public SearchQueryFacet(String name){
_name = name;
_maxFacets = -1;
_constraints = null;
_sort = FacetSort.none;
}
public SearchQueryFacet(String name, int maxFacets){
_name = name;
_maxFacets = maxFacets;
_constraints = null;
_sort = FacetSort.none;
}
public SearchQueryFacet(String name, int maxFacets, FacetSort sort){
_name = name;
_maxFacets = maxFacets;
_constraints = null;
_sort = sort;
}
public SearchQueryFacet(String name, int maxFacets, List<String> constraints){
_name = name;
_maxFacets = maxFacets;
_constraints = constraints;
_sort = FacetSort.none;
}
public SearchQueryFacet(String name, List<String> constraints){
_name = name;
_maxFacets = -1;
_constraints = constraints;
_sort = FacetSort.none;
}
public SearchQueryFacet(String name, FacetSort sort, List<String> constraints){
_name = name;
_maxFacets = -1;
_constraints = constraints;
_sort = sort;
}
public SearchQueryFacet(String name, FacetSort sort){
_name = name;
_maxFacets = -1;
_constraints = null;
_sort = sort;
}
public String getName() {
return _name;
}
public void setName(String name) {
_name = name;
}
public int getMaxFacets() {
return _maxFacets;
}
public void setMaxFacets(int maxFacets) {
_maxFacets = maxFacets;
}
public FacetSort getSort() {
return _sort;
}
public void setSort(FacetSort sort) {
_sort = sort;
}
public int get_maxFacets() {
return _maxFacets;
}
public void set_maxFacets(int _maxFacets) {
this._maxFacets = _maxFacets;
}
public List<String> getConstraints() {
return _constraints;
}
public void setConstraints(List<String> constraints) {
_constraints = constraints;
}
public void addConstraint(String constraint) {
if(_constraints == null)
_constraints = new LinkedList<String>();
_constraints.add(constraint);
}
@Override
public String toString(){
StringBuffer sb = new StringBuffer();
sb.append("&facet=");
sb.append(_name);
if(_maxFacets > 0){
sb.append("&facet-");
sb.append(_name);
sb.append("-top-n=");
sb.append(_maxFacets);
}
if((_constraints != null) && (_constraints.size() > 0)){
sb.append("&facet-");
sb.append(_name);
sb.append("-constraints=");
boolean first = true;
for(String c : _constraints){
if(!first)
sb.append("%2C");
else
first = false;
sb.append("%27");
sb.append(c);
sb.append("%27");
}
}
if(!_sort.equals(FacetSort.none)){
sb.append("&facet-");
sb.append(_name);
sb.append("-sort=");
sb.append(_sort);
}
return sb.toString();
}
public enum FacetSort{
none, alpha, count, max, sum
}
}
Listing 5 Facets control class
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