规则引擎编辑中的最重要的两个部分就是：模型model和商务规则business rule。比如说你的业务系统现在要增加一个字段fieldA，就会引起model的变化，新的规则就需要能够动态发现fieldA，并且能够支持fieldA的数据录入和校验，这样才算是动态的系统。
model的动态原理上很简单，就是动态生成Java类，drools中通过declare model来实现。原始的模型比较简单，效果如下：
我希望达到的效果是这样：
支持从XML Schema中选择对应的节点，同时在属性上能够更加丰富，支持正则表达式。为了达到这个效果，同时保持对原有的兼容，就需要创建一个新的资产（Asset）类型。
新增资产类型首先在contenthandler.properties文件中定义
# for models model.drl=org.drools.guvnor.server.contenthandler.drools.FactModelContentHandler # for new models mymodel.drl=org.drools.guvnor.server.contenthandler.drools.MyModelContentHandler
新定义的MyModelContentHandler是用来控制model和持久数据之间的访问的，参考FactModelContentHandler的写法，编写自己的实现。
public class MyModelContentHandler extends ContentHandler
implements
ICanRenderSource {
private static final LoggingHelper log = LoggingHelper.getLogger( FactModelContentHandler.class );
@Override
public void retrieveAssetContent(Asset asset,
AssetItem item) throws SerializationException {
try {
List<FactMetaModel> models = unmarshall( item.getContent() );
FactModels ms = new FactModels();
ms.models = models;
asset.setContent( ms );
} catch ( Exception e ) {
log.error( "Unable to parse the MyModel for the model - falling back to text (" + e.getMessage() + ")" );
RuleContentText text = new RuleContentText();
text.content = item.getContent();
asset.setContent( text );
}
}
@Override
public void storeAssetContent(Asset asset,
AssetItem repoAsset)
throws SerializationException {
if ( asset.getContent() instanceof FactModels ) {
FactModels fm = (FactModels) asset.getContent();
repoAsset.updateContent( marshall( fm.models ) );
} else {
RuleContentText text = (RuleContentText) asset.getContent();
repoAsset.updateContent( text.content );
}
}
public void assembleSource(PortableObject assetContent,
StringBuilder stringBuilder) {
FactModels fms = (FactModels) assetContent;
for ( FactMetaModel fm : fms.models ) {
stringBuilder.append( toDRL( fm ) );
stringBuilder.append( "\n\n" );
}
}
List<FactMetaModel> toModel(String drl) throws DroolsParserException {
if ( drl != null && (drl.startsWith( "#advanced" ) || drl.startsWith( "//advanced" )) ) {
throw new DroolsParserException( "Using advanced editor" );
}
DrlParser parser = new DrlParser();
PackageDescr pkg = parser.parse( drl );
if ( parser.hasErrors() ) {
throw new DroolsParserException( "The model drl " + drl + " is not valid" );
}
if ( pkg == null ) return new ArrayList<FactMetaModel>();
List<TypeDeclarationDescr> types = pkg.getTypeDeclarations();
List<FactMetaModel> list = new ArrayList<FactMetaModel>( types.size() );
for ( TypeDeclarationDescr td : types ) {
FactMetaModel mm = new FactMetaModel();
mm.setName( td.getTypeName() );
mm.setSuperType( td.getSuperTypeName() );
Map<String, TypeFieldDescr> fields = td.getFields();
for ( Map.Entry<String, TypeFieldDescr> en : fields.entrySet() ) {
String fieldName = en.getKey();
TypeFieldDescr descr = en.getValue();
FieldMetaModel fm = new FieldMetaModel( fieldName,
descr.getPattern().getObjectType(),
null,
null,
null,
null);
mm.getFields().add( fm );
}
list.add( mm );
}
return list;
}
public String marshall(List<FactMetaModel> models){
MyModelPersistence persistence = MyModelPersistence.getInstance();
StringBuilder sb = new StringBuilder();
sb.append("<Model>");
for ( FactMetaModel factMetaModel : models ) {
String str = persistence.marshal( factMetaModel );
sb.append( str ).append( "\n\n" );
}
sb.append("</Model>");
return sb.toString().trim();
}
public static List<FactMetaModel> unmarshall(String content){
String xml = content.replaceAll("<Model>", "").replace("</Model>", "");
MyModelPersistence persistence = MyModelPersistence.getInstance();
if(content == null || content.trim().length() == 0){
return new ArrayList<FactMetaModel>();
}
String[] strs = xml.split("\n\n");
List<FactMetaModel> list = new ArrayList<FactMetaModel>( strs.length );
for ( String str : strs ) {
FactMetaModel mm = persistence.unmarshal(str);
list.add( mm );
}
return list;
}
public static String toDRL(String content) {
List<FactMetaModel> models = unmarshall( content );
StringBuilder sb = new StringBuilder();
for ( FactMetaModel factMetaModel : models ) {
String drl = toDRL( factMetaModel );
sb.append( drl ).append( "\n\n" );
}
return sb.toString().trim();
}
/*
* 获得模型中的字段对应的中文显示名称
*/
public static Map<String, String> getDisplayNames(AssetItem item){
Map<String, String> displayNames = new HashMap<String, String>();
List<FactMetaModel> models = unmarshall( item.getContent() );
for ( FactMetaModel factMetaModel : models ) {
displayNames.put(factMetaModel.getName(), factMetaModel.getDisplayName());
for ( int i = 0; i < factMetaModel.getFields().size(); i++ ) {
FieldMetaModel f = factMetaModel.getFields().get( i );
displayNames.put(factMetaModel.getName() + "." + f.name, f.displayName);
}
}
return displayNames;
}
/*
* 获得模型中每个字段的限制正则表达式
*/
public static Map<String, String> getRestrictions(AssetItem item){
Map<String, String> regexs = new HashMap<String, String>();
List<FactMetaModel> models = unmarshall( item.getContent() );
for ( FactMetaModel factMetaModel : models ) {
for ( int i = 0; i < factMetaModel.getFields().size(); i++ ) {
FieldMetaModel f = factMetaModel.getFields().get( i );
regexs.put(factMetaModel.getName() + "." + f.name, f.regex);
}
}
return regexs;
}
/*
* 将FactMetaModel翻译成DRL文件
*/
static String toDRL(FactMetaModel mm) {
StringBuilder sb = new StringBuilder();
sb.append( "declare " ).append( mm.getName() );
if ( mm.hasSuperType() ) {
sb.append( " extends " );
sb.append( mm.getSuperType() );
}
for ( int i = 0; i < mm.getFields().size(); i++ ) {
FieldMetaModel f = mm.getFields().get( i );
sb.append( "\n\t" );
sb.append( f.name ).append( ": " ).append( f.type );
}
sb.append( "\nend" );
return sb.toString();
}
/*
* 获得模型中每个字段的修饰操作标记，可以是可读写的、只读、只写状态
*/
public static Map<String, FieldAccessorsAndMutators> getAccessorsAndMutators(
AssetItem as) {
Map<String, FieldAccessorsAndMutators> fieldAccessors = new HashMap<String, FieldAccessorsAndMutators>();
List<FactMetaModel> models = unmarshall( as.getContent() );
for ( FactMetaModel factMetaModel : models ) {
for ( int i = 0; i < factMetaModel.getFields().size(); i++ ) {
FieldMetaModel f = factMetaModel.getFields().get( i );
FieldAccessorsAndMutators accessor;
if(f.scope.equals("when")){
accessor = FieldAccessorsAndMutators.ACCESSOR;
}else if(f.scope.equals("then")){
accessor = FieldAccessorsAndMutators.MUTATOR;
}else{
accessor = FieldAccessorsAndMutators.BOTH;
}
fieldAccessors.put(factMetaModel.getName() + "." + f.name, accessor);
}
}
return fieldAccessors;
}
}
相应的模型定义为
/**
* Represents the GUI data for a fact model definition.
*/
public class FactMetaModel
implements
PortableObject {
private static final long serialVersionUID = 510L;
private String name;
private String displayName;
private String superType;
private List<FieldMetaModel> fields = new ArrayList<FieldMetaModel>();
//List reference schema by this fact
private List<String[]> schemas = new ArrayList<String[]>();
public List<String[]> getSchemas() {
return schemas;
}
public void setSchemas(List<String[]> schemas) {
this.schemas = schemas;
}
public FactMetaModel() {
}
public FactMetaModel(String name, String displayName) {
this.name = name;
this.displayName = displayName;
}
public FactMetaModel(String name,
String displayName,
List<FieldMetaModel> fields) {
this.name = name;
this.displayName = displayName;
this.fields = fields;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDisplayName() {
return displayName;
}
public void setDisplayName(String displayName) {
this.displayName = displayName;
}
public List<FieldMetaModel> getFields() {
return fields;
}
public void setFields(List<FieldMetaModel> fields) {
this.fields = fields;
}
public void setSuperType(String superType) {
this.superType = superType;
}
public String getSuperType() {
return this.superType;
}
public boolean hasSuperType() {
return this.superType != null;
}
}
这样，后台和数据层的交道就差不多了，下一篇我们介绍如何在前端实现增强的效果。