對(duì)于現(xiàn)在越來越輕量級(jí)，越來越講究速度和接近用戶的應(yīng)用來說，xml確實(shí)有點(diǎn)復(fù)雜了。解析起來不僅耗內(nèi)存，而且很復(fù)雜。這就好像花了幾千塊錢買了個(gè)MS Office，但是80%的feature都用不著，還白白的耗著CPU和內(nèi)存。
個(gè)人覺得，設(shè)置文件用XML其實(shí)挺好，因?yàn)樵O(shè)置文件一般并不太大，而且要求可讀性強(qiáng)，還有很多亂七八糟的需求，可以利用XML的力量。昨天搞chrome的設(shè)置，發(fā)現(xiàn)chrome的設(shè)置文件也是使用的json，讀起來也是輕松愉快。
前陣子做了個(gè)程序，需要解析豆瓣API調(diào)用返回的XML。真想說一句。。。豆瓣你別用XML了。。。至少，提供個(gè)json版的API調(diào)用吧。
（以上謹(jǐn)代表個(gè)人觀點(diǎn)）
===================正文=================
解析豆瓣返回的xml，實(shí)在是不想用DOM這個(gè)重量級(jí)的玩意。DOM這個(gè)玩意，說它強(qiáng)大好還是說它官僚好呢。我傾向于使用SAXP解析。但是現(xiàn)在面臨的一個(gè)問題是，我需要根據(jù)xml節(jié)點(diǎn)的名字和屬性值（一個(gè)或者多個(gè)）來決定當(dāng)前的值是不是我想要的。這就麻煩一點(diǎn)點(diǎn)。第一反應(yīng)是考慮xpath。后來覺得不如自己做一個(gè)得了，權(quán)當(dāng)是按需定制一個(gè)輕量級(jí)的xpath。
首先定義XMLSearchUnit類，這個(gè)類的實(shí)例用來描述一個(gè)需要在XML中搜索的值，值可以是xml節(jié)點(diǎn)的值，或者是節(jié)點(diǎn)的屬性。
package com.deepnighttwo.resourceresolver.douban.resolver.utils;
import java.util.HashMap;
import java.util.Map;
import org.xml.sax.Attributes;
/**
*
* Represent a search task. Target could be value of a node or attribute of the
* node.
*
* @author mzang
*/
publicclass XMLSearchUnit {
// attribute values to be matched during search
private Map<String, String> attributeMatchValidation =new HashMap<String, String>();
// if target is an attribute, then set this member to be the attribute name.
// if it is null or empty, then means the target is node value.
private String expectedAttr;
// xml path, format is: /node_name/node_name/...
private String xmlPath;
public XMLSearchUnit(String xmlPath) {
this.xmlPath = xmlPath;
}
/**
* if current node meets the search conditions or not. Meets means the path
* is correct and the attribute value is matched.
*
* @param path
* @param attributes
* @return
*/
publicboolean match(String path, Attributes attributes) {
if (xmlPath.equals(path) ==false) {
returnfalse;
}
for (String key : attributeMatchValidation.keySet()) {
String exp = attributeMatchValidation.get(key);
String compare = attributes.getValue(key);
if (exp.equalsIgnoreCase(compare) ==false) {
returnfalse;
}
}
returntrue;
}
public Map<String, String> getAttributeMatchValidation() {
return attributeMatchValidation;
}
publicvoid addAttributeValidation(String key, String value) {
attributeMatchValidation.put(key, value);
}
public String getXmlPath() {
return xmlPath;
}
publicvoid setAttributeMatchValidation(
Map<String, String> attributeMatchValidation) {
this.attributeMatchValidation = attributeMatchValidation;
}
public String getExpectedAttr() {
return expectedAttr;
}
/**
* if target is node value, then set expectedAttr to null. if target is an
* attribute value, set it to be the attribute name.
*
* @param expectedAttr
*/
publicvoid setExpectedAttr(String expectedAttr) {
this.expectedAttr = expectedAttr;
}
/**
* hash code can be cached if all properties are not be be changed.
*/
@Override
publicint hashCode() {
finalint prime =31;
int result =1;
result = prime
* result
+ ((attributeMatchValidation ==null) ?0
: attributeMatchValidation.hashCode());
result = prime * result
+ ((expectedAttr ==null) ?0 : expectedAttr.hashCode());
result = prime * result + ((xmlPath ==null) ?0 : xmlPath.hashCode());
return result;
}
@Override
publicboolean equals(Object obj) {
if (this== obj)
returntrue;
if (obj ==null)
returnfalse;
if (getClass() != obj.getClass())
returnfalse;
XMLSearchUnit other = (XMLSearchUnit) obj;
if (attributeMatchValidation ==null) {
if (other.attributeMatchValidation !=null)
returnfalse;
} elseif (!attributeMatchValidation
.equals(other.attributeMatchValidation))
returnfalse;
if (expectedAttr ==null) {
if (other.expectedAttr !=null)
returnfalse;
} elseif (!expectedAttr.equals(other.expectedAttr))
returnfalse;
if (xmlPath ==null) {
if (other.xmlPath !=null)
returnfalse;
} elseif (!xmlPath.equals(other.xmlPath))
returnfalse;
returntrue;
}
}
import java.util.HashMap;
import java.util.Map;
import org.xml.sax.Attributes;
/**
*
* Represent a search task. Target could be value of a node or attribute of the
* node.
*
* @author mzang
*/
publicclass XMLSearchUnit {
// attribute values to be matched during search
private Map<String, String> attributeMatchValidation =new HashMap<String, String>();
// if target is an attribute, then set this member to be the attribute name.
// if it is null or empty, then means the target is node value.
private String expectedAttr;
// xml path, format is: /node_name/node_name/...
private String xmlPath;
public XMLSearchUnit(String xmlPath) {
this.xmlPath = xmlPath;
}
/**
* if current node meets the search conditions or not. Meets means the path
* is correct and the attribute value is matched.
*
* @param path
* @param attributes
* @return
*/
publicboolean match(String path, Attributes attributes) {
if (xmlPath.equals(path) ==false) {
returnfalse;
}
for (String key : attributeMatchValidation.keySet()) {
String exp = attributeMatchValidation.get(key);
String compare = attributes.getValue(key);
if (exp.equalsIgnoreCase(compare) ==false) {
returnfalse;
}
}
returntrue;
}
public Map<String, String> getAttributeMatchValidation() {
return attributeMatchValidation;
}
publicvoid addAttributeValidation(String key, String value) {
attributeMatchValidation.put(key, value);
}
public String getXmlPath() {
return xmlPath;
}
publicvoid setAttributeMatchValidation(
Map<String, String> attributeMatchValidation) {
this.attributeMatchValidation = attributeMatchValidation;
}
public String getExpectedAttr() {
return expectedAttr;
}
/**
* if target is node value, then set expectedAttr to null. if target is an
* attribute value, set it to be the attribute name.
*
* @param expectedAttr
*/
publicvoid setExpectedAttr(String expectedAttr) {
this.expectedAttr = expectedAttr;
}
/**
* hash code can be cached if all properties are not be be changed.
*/
@Override
publicint hashCode() {
finalint prime =31;
int result =1;
result = prime
* result
+ ((attributeMatchValidation ==null) ?0
: attributeMatchValidation.hashCode());
result = prime * result
+ ((expectedAttr ==null) ?0 : expectedAttr.hashCode());
result = prime * result + ((xmlPath ==null) ?0 : xmlPath.hashCode());
return result;
}
@Override
publicboolean equals(Object obj) {
if (this== obj)
returntrue;
if (obj ==null)
returnfalse;
if (getClass() != obj.getClass())
returnfalse;
XMLSearchUnit other = (XMLSearchUnit) obj;
if (attributeMatchValidation ==null) {
if (other.attributeMatchValidation !=null)
returnfalse;
} elseif (!attributeMatchValidation
.equals(other.attributeMatchValidation))
returnfalse;
if (expectedAttr ==null) {
if (other.expectedAttr !=null)
returnfalse;
} elseif (!expectedAttr.equals(other.expectedAttr))
returnfalse;
if (xmlPath ==null) {
if (other.xmlPath !=null)
returnfalse;
} elseif (!xmlPath.equals(other.xmlPath))
returnfalse;
returntrue;
}
}
這個(gè)類比較簡單。就是用一個(gè)hashmap保待匹配的attribut鍵值對(duì)，用一個(gè)字符串表示期待的attribute name，用一個(gè)字符串表示期待的node path。
然后就是如何在SAXP里用到這個(gè)類的實(shí)例去搜索了。
package com.deepnighttwo.resourceresolver.douban.resolver.utils;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
/**
*
* SAXP parser working with XMLSearchUnit.
*
* @author mzang
*/
publicclass DoubanSearchParser extends DefaultHandler {
// create and initial search units
publicstaticfinal XMLSearchUnit DETAILS_LINK_API_PATH =new XMLSearchUnit(
"/feed/entry/id");
publicstaticfinal XMLSearchUnit DETAILS_CONTENT_PATH =new XMLSearchUnit(
"/entry/summary");
publicstaticfinal XMLSearchUnit DETAILS_TITLE_PATH =new XMLSearchUnit(
"/entry/title");
publicstaticfinal XMLSearchUnit DETAILS_CHINESE_NAME_PATH =new XMLSearchUnit(
"/entry/db:attribute");
publicstaticfinal XMLSearchUnit DETAILS_RATINGE_PATH =new XMLSearchUnit(
"/entry/gd:rating");
publicstaticfinal XMLSearchUnit DETAILS_RATINGE_RATER_COUNT_PATH =new XMLSearchUnit(
"/entry/gd:rating");
publicstaticfinal XMLSearchUnit DETAILS_LINK_URL_PATH =new XMLSearchUnit(
"/feed/entry/link");
static {
DETAILS_LINK_URL_PATH.addAttributeValidation("rel", "alternate");
DETAILS_LINK_URL_PATH.setExpectedAttr("href");
DETAILS_CHINESE_NAME_PATH.addAttributeValidation("lang", "zh_CN");
DETAILS_CHINESE_NAME_PATH.addAttributeValidation("name", "aka");
DETAILS_RATINGE_PATH.setExpectedAttr("average");
DETAILS_RATINGE_RATER_COUNT_PATH.setExpectedAttr("numRaters");
}
// a map to store the XMLSearchUnit and value
private Map<XMLSearchUnit, String> results =new HashMap<XMLSearchUnit, String>();
// a counter of search unit. if it is 0, then all search unit finds a match
// value and the result of the XML will be skipped.
privateint count =0;
private StringBuilder path =new StringBuilder();
privatestaticfinal String pathSeparater ="/";
private XMLSearchUnit[] searchUnits;
List<XMLSearchUnit> foundItems =new ArrayList<XMLSearchUnit>();
/**
* constructor, accept XML input stream, 0 or more search unit instances.
*
* @param input
* @param expectedPath
* @return
*/
public Map<XMLSearchUnit, String> parseResults(InputStream input,
XMLSearchUnit... expectedPath) {
for (XMLSearchUnit search : expectedPath) {
results.put(search, null);
}
searchUnits = expectedPath;
count = expectedPath.length;
XMLReader xmlReader =null;
try {
SAXParserFactory spfactory = SAXParserFactory.newInstance();
spfactory.setValidating(false);
SAXParser saxParser = spfactory.newSAXParser();
xmlReader = saxParser.getXMLReader();
xmlReader.setContentHandler(this);
xmlReader.parse(new InputSource(input));
} catch (Exception e) {
System.err.println(e);
System.exit(1);
}
return results;
}
privatevoid addToPath(String addPath) {
path.append(pathSeparater).append(addPath.toLowerCase());
}
privatevoid popPath() {
int index = path.lastIndexOf(pathSeparater);
// String removedPath = path.substring(index);
path.delete(index, path.length());
}
@Override
publicvoid startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException {
foundItems.clear();
if (count ==0) {
return;
}
// update path
addToPath(qName);
List<XMLSearchUnit> foundAttrItems =null;
// check if current node matches search units. if it is a node value
// search, then store it in a member variable named foundItems because
// the value of the node is known only when reaches the end of the
// node.but for attribute search, it value is known here. So then are
// put in a local variable list named foundAttrItems.
for (XMLSearchUnit unit : searchUnits) {
if (unit.match(path.toString(), attributes) ==true) {
if (unit.getExpectedAttr() ==null) {
foundItems.add(unit);
} else {
if (foundAttrItems ==null) {
foundAttrItems =new ArrayList<XMLSearchUnit>();
}
foundAttrItems.add(unit);
}
}
}
// if no attribute match, return.
if (foundAttrItems ==null) {
return;
}
// fill search unit value using attribute value. update count.
for (XMLSearchUnit attrUnit : foundAttrItems) {
String attrValue = attributes.getValue(attrUnit.getExpectedAttr());
if (results.get(attrUnit) ==null) {
count--;
}
results.put(attrUnit, attrValue);
count--;
}
}
/**
* if current node matches, the the node value is useful, store it.
*/
@Override
publicvoid characters(char[] ch, int start, int length)
throws SAXException {
if (count ==0) {
return;
}
if (foundItems.size() ==0) {
return;
}
for (XMLSearchUnit unit : foundItems) {
String content =new String(ch, start, length);
if (results.get(unit) ==null) {
count--;
}
results.put(unit, content);
}
}
@Override
publicvoid endElement(String uri, String localName, String qName)
throws SAXException {
foundItems.clear();
if (count ==0) {
return;
}
popPath();
}
}
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
/**
*
* SAXP parser working with XMLSearchUnit.
*
* @author mzang
*/
publicclass DoubanSearchParser extends DefaultHandler {
// create and initial search units
publicstaticfinal XMLSearchUnit DETAILS_LINK_API_PATH =new XMLSearchUnit(
"/feed/entry/id");
publicstaticfinal XMLSearchUnit DETAILS_CONTENT_PATH =new XMLSearchUnit(
"/entry/summary");
publicstaticfinal XMLSearchUnit DETAILS_TITLE_PATH =new XMLSearchUnit(
"/entry/title");
publicstaticfinal XMLSearchUnit DETAILS_CHINESE_NAME_PATH =new XMLSearchUnit(
"/entry/db:attribute");
publicstaticfinal XMLSearchUnit DETAILS_RATINGE_PATH =new XMLSearchUnit(
"/entry/gd:rating");
publicstaticfinal XMLSearchUnit DETAILS_RATINGE_RATER_COUNT_PATH =new XMLSearchUnit(
"/entry/gd:rating");
publicstaticfinal XMLSearchUnit DETAILS_LINK_URL_PATH =new XMLSearchUnit(
"/feed/entry/link");
static {
DETAILS_LINK_URL_PATH.addAttributeValidation("rel", "alternate");
DETAILS_LINK_URL_PATH.setExpectedAttr("href");
DETAILS_CHINESE_NAME_PATH.addAttributeValidation("lang", "zh_CN");
DETAILS_CHINESE_NAME_PATH.addAttributeValidation("name", "aka");
DETAILS_RATINGE_PATH.setExpectedAttr("average");
DETAILS_RATINGE_RATER_COUNT_PATH.setExpectedAttr("numRaters");
}
// a map to store the XMLSearchUnit and value
private Map<XMLSearchUnit, String> results =new HashMap<XMLSearchUnit, String>();
// a counter of search unit. if it is 0, then all search unit finds a match
// value and the result of the XML will be skipped.
privateint count =0;
private StringBuilder path =new StringBuilder();
privatestaticfinal String pathSeparater ="/";
private XMLSearchUnit[] searchUnits;
List<XMLSearchUnit> foundItems =new ArrayList<XMLSearchUnit>();
/**
* constructor, accept XML input stream, 0 or more search unit instances.
*
* @param input
* @param expectedPath
* @return
*/
public Map<XMLSearchUnit, String> parseResults(InputStream input,
XMLSearchUnit... expectedPath) {
for (XMLSearchUnit search : expectedPath) {
results.put(search, null);
}
searchUnits = expectedPath;
count = expectedPath.length;
XMLReader xmlReader =null;
try {
SAXParserFactory spfactory = SAXParserFactory.newInstance();
spfactory.setValidating(false);
SAXParser saxParser = spfactory.newSAXParser();
xmlReader = saxParser.getXMLReader();
xmlReader.setContentHandler(this);
xmlReader.parse(new InputSource(input));
} catch (Exception e) {
System.err.println(e);
System.exit(1);
}
return results;
}
privatevoid addToPath(String addPath) {
path.append(pathSeparater).append(addPath.toLowerCase());
}
privatevoid popPath() {
int index = path.lastIndexOf(pathSeparater);
// String removedPath = path.substring(index);
path.delete(index, path.length());
}
@Override
publicvoid startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException {
foundItems.clear();
if (count ==0) {
return;
}
// update path
addToPath(qName);
List<XMLSearchUnit> foundAttrItems =null;
// check if current node matches search units. if it is a node value
// search, then store it in a member variable named foundItems because
// the value of the node is known only when reaches the end of the
// node.but for attribute search, it value is known here. So then are
// put in a local variable list named foundAttrItems.
for (XMLSearchUnit unit : searchUnits) {
if (unit.match(path.toString(), attributes) ==true) {
if (unit.getExpectedAttr() ==null) {
foundItems.add(unit);
} else {
if (foundAttrItems ==null) {
foundAttrItems =new ArrayList<XMLSearchUnit>();
}
foundAttrItems.add(unit);
}
}
}
// if no attribute match, return.
if (foundAttrItems ==null) {
return;
}
// fill search unit value using attribute value. update count.
for (XMLSearchUnit attrUnit : foundAttrItems) {
String attrValue = attributes.getValue(attrUnit.getExpectedAttr());
if (results.get(attrUnit) ==null) {
count--;
}
results.put(attrUnit, attrValue);
count--;
}
}
/**
* if current node matches, the the node value is useful, store it.
*/
@Override
publicvoid characters(char[] ch, int start, int length)
throws SAXException {
if (count ==0) {
return;
}
if (foundItems.size() ==0) {
return;
}
for (XMLSearchUnit unit : foundItems) {
String content =new String(ch, start, length);
if (results.get(unit) ==null) {
count--;
}
results.put(unit, content);
}
}
@Override
publicvoid endElement(String uri, String localName, String qName)
throws SAXException {
foundItems.clear();
if (count ==0) {
return;
}
popPath();
}
}
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