Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
	at com.weir.mgen.configure.implementors.xmlimpl.RootConfXmlImpl.readNeedGens(RootConfXmlImpl.java:56)
	at com.weir.mgen.configure.implementors.xmlimpl.RootConfXmlImpl.getNeedGens(RootConfXmlImpl.java:21)
	at com.weir.mgen.configure.manage.ConfManage.readRootConf(ConfManage.java:74)
	at com.weir.mgen.configure.manage.ConfManage.readConf(ConfManage.java:33)
	at com.weir.mgen.configure.manage.ConfManage.<init>(ConfManage.java:16)
	at com.weir.mgen.configure.manage.ConfManage.getInstance(ConfManage.java:21)
	at com.weir.mgen.configure.RootConfImpl.getGenConf(RootConfImpl.java:29)
	at com.weir.test.MyTest.main(MyTest.java:33)

程序为：

package com.weir.mgen.configure.implementors.xmlimpl;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.weir.mgen.configure.implementors.RootConfImplementor;
import com.weir.mgen.configure.implementors.ThemeConfImplementor;
import com.weir.mgen.configure.vo.NeedGenModel;
import com.weir.mgen.configure.vo.ThemeModel;
import com.weir.mgen.constants.ExpressionEnum;
import com.weir.mgen.util.readxml.Context;
import com.weir.mgen.util.readxml.ReadXmlExpression;
import com.weir.mgen.util.readxml.parser.Parser;

public class RootConfXmlImpl implements RootConfImplementor{

	@Override
	public List<NeedGenModel> getNeedGens() {
		return readNeedGens();
	}

	@Override
	public List<ThemeModel> getThemes() {
		return readThemes();
	}

	@Override
	public Map<String, String> getMapconstants() {
		return readMapconstants();
	}
	private Context getContext(){
		Context c = null;
		try {
			//System.out.println(new RootConfBuilder().addXmlFilePre().addGenConf().addDot().addXml().build());
			c= Context.getInstance(new RootConfBuilder().addXmlFilePre().addGenConf().addDot().addXml().build());
		} catch (Exception e) {
			e.printStackTrace();
		}
		return c;
	}

	private List<NeedGenModel> readNeedGens() {
		List<NeedGenModel> list = new ArrayList<NeedGenModel>();
		
		Context c = this.getContext();
		
		String[] needGenIds = parseNeedGenIds(c);
		String[] needProviders = parseNeedGenProviders(c);
		String[] needThemeIds = parseNeedGenThemeIds(c);
		
		for (int i = 0; i < needGenIds.length; i++) {
			NeedGenModel ngm = new NeedGenModel();
			ngm.setId(needGenIds[i]);
			ngm.setProvider(needProviders[i]);
			ngm.setTheme(needThemeIds[i]);
			
			String[] paramIds = parseParamIds(c, ngm.getId());
			String[] paramValues = parseParamValues(c, ngm.getId());
			
			Map<String, String> map = new HashMap<String, String>();
			for (int j = 0; j < paramIds.length; j++) {
				map.put(paramIds[j], paramValues[j]);
			}
			ngm.setMapParams(map);
			list.add(ngm);
		}
		
		return list;
	}

	private String[] parseNeedGenIds(Context c) {
		c.init();
		//genconf/needgens/needgen$.id$
		ReadXmlExpression re = Parser.parser(new RootConfBuilder().addGenConf().addSeparator().addNeedGens().addSeparator()
				.addNeedGen().addDollar().addDot().addId().addDollar().build());
		return re.interpret(c);
	}
	
	private String[] parseNeedGenProviders(Context c) {
		c.init();
//		System.out.println("11111111111===="+new RootConfBuilder().addGenConf().addSeparator().addNeedGens().addSeparator()
//				.addNeedGen().addDollar().addDot().addProvider().addDollar().build());
		ReadXmlExpression re = Parser.parser(new RootConfBuilder().addGenConf().addSeparator().addNeedGens().addSeparator()
				.addNeedGen().addDollar().addDot().addProvider().addDollar().build());
		return re.interpret(c);
	}
	private String[] parseNeedGenThemeIds(Context c) {
		c.init();
		ReadXmlExpression re = Parser.parser(new RootConfBuilder().addGenConf().addSeparator().addNeedGens().addSeparator()
				.addNeedGen().addDollar().addDot().addThemeId().addDollar().build());
		return re.interpret(c);
	}
	private String[] parseParamIds(Context c,String needGenId) {
		c.init();
		ReadXmlExpression re = Parser.parser(new RootConfBuilder().addGenConf().addSeparator().addNeedGens().addSeparator()
				.addNeedGen().addDollar()
				.addOpenBracket().addId().addEqual().addOtherValue(needGenId).addCloseBracket()
				.addSeparator().addParams().addDollar().addSeparator().addParam().addDollar()
				.addDot().addId().addDollar().build());
		return re.interpret(c);
	}
	private String[] parseParamValues(Context c,String neefGenId) {
		c.init();
		ReadXmlExpression re = Parser.parser(new RootConfBuilder().addGenConf().addSeparator().addNeedGens().addSeparator()
				.addNeedGen().addDollar().addOpenBracket().addId().addEqual().addOtherValue(neefGenId)
				.addCloseBracket().addSeparator().addParams().addDollar().addSeparator().addParam().addDollar()
				.build());
		return re.interpret(c);
	}
	
	////////////////////////////////////////////////////
	private List<ThemeModel> readThemes() {
		List<ThemeModel> themeModels = new ArrayList<ThemeModel>();
		Context c = this.getContext();
		
		String[] ids = parseThemeIds(c);
		String[] locations = parseLocations(c);
		
		for (int i = 0; i < ids.length; i++) {
            ThemeModel tm = new ThemeModel();
			
			tm.setId(ids[i]);
			tm.setLocation(locations[i]);
			
			ThemeConfImplementor thImpl = new ThemeConfXmlImpl();
			
			Map<String, String> params = new HashMap<String,String>();
			params.put(ExpressionEnum.location.getExpr(), locations[i]);
			
			tm.setMapGenOutTypes(thImpl.getMapGenOutTypes(ids[i], params));
			tm.setMapGenTypes(thImpl.getMapGenTypes(ids[i], params));
			tm.setMapProviders(thImpl.getMapProviders(ids[i], params));
			
			themeModels.add(tm);
		}
		return themeModels;
	}
	
	private String[] parseThemeIds(Context c) {
		c.init();
		ReadXmlExpression re = Parser.parser(new RootConfBuilder().addGenConf().addSeparator().addThemes().addSeparator()
				.addTheme().addDollar().addDot().addId().addDollar().build());
		return re.interpret(c);
	}
	private String[] parseLocations(Context c) {
		c.init();
		ReadXmlExpression re = Parser.parser(new RootConfBuilder().addGenConf().addSeparator().addThemes().addSeparator()
				.addTheme().addDollar().build());
		return re.interpret(c);
	}
	
	//////////////////////////////////////////////////////
	private Map<String, String> readMapconstants() {
		Map<String, String> map = new HashMap<String,String>();
		Context c = this.getContext();
		
		String[] ids = parseConstantIds(c);
		String[] values = parseConstantValues(c);
		
		for (int i = 0; i < ids.length; i++) {
			map.put(ids[i], values[i]);
		}
		
		return map;
	}
	
	private String[] parseConstantIds(Context c) {
		c.init();
		ReadXmlExpression re = Parser.parser(new RootConfBuilder().addGenConf().addSeparator().addConstants().addSeparator()
				.addConstant().addDollar().addDot().addId().addDollar().build());
		return re.interpret(c);
	}
	private String[] parseConstantValues(Context c) {
		c.init();
		ReadXmlExpression re = Parser.parser(new RootConfBuilder().addGenConf().addSeparator().addConstants().addSeparator()
				.addConstant().addDollar().build());
		return re.interpret(c);
	}
}

不知道为什么会出这样的错误？ 请老师看看，谢谢