为什么我的 class 构造函数被重复调用？
Why is my class constructor called repeatedly?
最近我一直在研究一个程序，可以将 TeX 生成的 PDF 转换为某种形式的文本，保留一些语义上有意义的样式信息，例如下标和上标。
在调试时，似乎 PDFTextStripper class.
可能发生了一些非常不寻常的事情
这是我的 TeXUtil class 完成的大部分工作。
import com.google.common.base.CharMatcher;
import org.apache.pdfbox.pdmodel.font.PDFont;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.IOException;
import java.util.Hashtable;
import java.util.Stack;
public class TeXUtil {
private Stack<SSStatus> ssstatus;
private boolean accentMode;
private String fs;
private boolean mathMode;
private SymbolDB db;
private Hashtable<String, String> maccDict;
float endY;//Positions
float endX;
float Y;
int height;//Height
//boolean test;
public TeXUtil() throws IOException {
ssstatus = new Stack<SSStatus>();
fs = "rm";
accentMode = false;//as in the state of being right after an accent
mathMode = false;
db = new SymbolDB();
maccDict = new Hashtable<String, String>();
maccDict.put("\vec","\vec");
maccDict.put("\widehat","\widehat");
maccDict.put("\widetilde","\widetilde");
maccDict.put("\^","\hat");
maccDict.put("\v","\check");
maccDict.put("\u","\breve");
maccDict.put("\`","\grave");
maccDict.put("\~","\tilde");
maccDict.put("\=","\bar");
maccDict.put("\.","\dot");
maccDict.put("\","\ddot");
maccDict.put("\'","\acute");
endY = 0;
endX = 0;
Y = 0;
height = 0;
//test = false;
System.out.println("TeXUtil initialized!");
}
private static String fontShortName(PDFont font) {
String[] segments = font.getName().split("\+");
return segments[segments.length - 1];
}
private static int fontHeight(PDFont font) {
CharMatcher matcher = CharMatcher.inRange('0', '9');
return Integer.parseInt(matcher.retainFrom(fontShortName(font)));
}
private static String fontClass(PDFont font) {
CharMatcher matcher = CharMatcher.inRange('A', 'Z');
return (matcher.retainFrom(fontShortName(font))).toLowerCase();
}
private String textToTeX(String shortFontName, int code) throws JSONException {
JSONObject info = db.getInfo(shortFontName, code);
return info.getString("value");
}
public String fullTextToTeX(PDFont font, int code, float newEndX, float newY, float newEndY){
String shortFontName = fontClass(font);
try {
JSONObject info = db.getInfo(shortFontName, code);
String teXCode = info.getString("value");
StringBuilder preamble1 = new StringBuilder("");
StringBuilder preamble2 = new StringBuilder("");
StringBuilder postamble = new StringBuilder("");
boolean text = info.getBoolean("text");
boolean math = info.getBoolean("math");
boolean tacc = info.getBoolean("tacc");
boolean macc = info.getBoolean("macc");
String newFont = info.getString("font");
int newHeight = fontHeight(font);
//Font change, rm is seen as having no font
if (!newFont.equals(fs)) {
if (!fs.equals("rm"))
preamble1.insert(0, '}');
if (!newFont.equals("rm")) {
preamble2.append('\');
preamble2.append(newFont);
preamble2.append('{');
}
preamble1.insert(0, " fs = " + fs + " nFs = " + newFont + "\n");
fs = newFont;
}
if (height == 0) {
//preamble2.append(" Meow! am = " + accentMode + " fs = " + fs + " mm = " + mathMode + "\n");
}
//Subscripts/Superscripts
if (height > newHeight && newEndX > endX) {//New subscript/superscript
if (newEndY < endY) {//New superscript
//ssstatus.push(SSStatus.SUP);
preamble2.insert(0, "^{");
}
else if (newY > Y) {//New subscript
//ssstatus.push(SSStatus.SUB);
preamble2.insert(0, "_{");
}
//else {
// System.out.println("Please investigate the situation: texcode = " + teXCode + "endY = " + endY + " Y=" + Y + " endX=" + endX + " newEndY=" + newEndY + " newY=" + newY + " newEndX= " + newEndX);
//}
}
else if (height < newHeight && height != 0) {
//ssstatus.pop();
preamble1.append('}');
}
height = newHeight;
endX = newEndX;
endY = newEndY;
Y = newY;
//Enter or leave math mode
if (mathMode && !math && !macc) {
mathMode = false;
preamble1.append('$');
}
else if (!mathMode && !text && !tacc) {
mathMode = true;
preamble2.insert(0,'$');
}
//Accents
if (accentMode) {//If accent mode is ever entered we need to leave it at once
postamble.append('}');
accentMode = false;
}
if ((mathMode && macc) || (!mathMode && tacc)) {//Right now assume that anything that can be an accent is an accent
postamble.append('{');
if (mathMode)
teXCode = maccDict.get(teXCode);
accentMode = true;
}
if (teXCode.charAt(0) == '\')
return preamble1.toString() + preamble2.toString() + teXCode + ' ' + postamble.toString();
else
return preamble1.toString() + preamble2.toString() + teXCode + postamble.toString();
}
catch(JSONException e) {
return "\" + shortFontName + "{" + code + "}";
}
}
}
这里是主要内容class。
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.font.PDFont;
import org.apache.pdfbox.text.PDFTextStripper;
import org.apache.pdfbox.text.TextPosition;
import com.google.common.base.CharMatcher;
import org.json.*;
import java.io.File;
import java.io.IOException;
import java.util.List;
import java.util.Stack;
public class TEX2TXT {
public static void main(String args[]) throws IOException {
TeXUtil util = new TeXUtil();
//Loading an existing document
File file = new File("/Users/CatLover/Documents/Tex/Examples/c4.pdf");
PDDocument document = PDDocument.load(file);
//Instantiate PDFTextStripper class
PDFTextStripper pdfStripper = new PDFTextStripper() {
protected void writeString(String text, List<TextPosition> textPositions) throws IOException {
TeXUtil util = new TeXUtil();
StringBuilder builder = new StringBuilder();
for(TextPosition position: textPositions) {
float Y = position.getY();
float endY = position.getEndY();
float endX = position.getEndX();
PDFont font = position.getFont();
int[] codes = position.getCharacterCodes();
for(int code: codes) {
builder.append(util.fullTextToTeX(font, code, endX, Y, endY));
}
}
writeString(builder.toString());
}
};
//Retrieving text from PDF document
String text = pdfStripper.getText(document);
System.out.println(text);
//Closing the document
document.close();
}
真正奇怪的是，TeXUtil 是在每次单词之间出现白色 space 时构造的，而 TeXUtil() 应该只调用一次。我不确定为什么会这样。由于 PDF 是由 LaTeX 生成的，而 LaTeX 不会在 PDF 中放置白色 space 字符，而是在字符之间留下 space 以隐式表示白色 space，这可能会影响 PDFBox 的工作方式。
您正在 PDFTextStripper 子类的 writeString 方法的第一行中构造一个新的 TeXUtil。如果您只是删除该行，它应该仍然可以引用您的 main 方法中定义的 util （尽管根据您使用的 java 的版本，您可能必须将其设为 final).
最近我一直在研究一个程序，可以将 TeX 生成的 PDF 转换为某种形式的文本，保留一些语义上有意义的样式信息，例如下标和上标。
在调试时，似乎 PDFTextStripper class.
这是我的 TeXUtil class 完成的大部分工作。
import com.google.common.base.CharMatcher;
import org.apache.pdfbox.pdmodel.font.PDFont;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.IOException;
import java.util.Hashtable;
import java.util.Stack;
public class TeXUtil {
private Stack<SSStatus> ssstatus;
private boolean accentMode;
private String fs;
private boolean mathMode;
private SymbolDB db;
private Hashtable<String, String> maccDict;
float endY;//Positions
float endX;
float Y;
int height;//Height
//boolean test;
public TeXUtil() throws IOException {
ssstatus = new Stack<SSStatus>();
fs = "rm";
accentMode = false;//as in the state of being right after an accent
mathMode = false;
db = new SymbolDB();
maccDict = new Hashtable<String, String>();
maccDict.put("\vec","\vec");
maccDict.put("\widehat","\widehat");
maccDict.put("\widetilde","\widetilde");
maccDict.put("\^","\hat");
maccDict.put("\v","\check");
maccDict.put("\u","\breve");
maccDict.put("\`","\grave");
maccDict.put("\~","\tilde");
maccDict.put("\=","\bar");
maccDict.put("\.","\dot");
maccDict.put("\","\ddot");
maccDict.put("\'","\acute");
endY = 0;
endX = 0;
Y = 0;
height = 0;
//test = false;
System.out.println("TeXUtil initialized!");
}
private static String fontShortName(PDFont font) {
String[] segments = font.getName().split("\+");
return segments[segments.length - 1];
}
private static int fontHeight(PDFont font) {
CharMatcher matcher = CharMatcher.inRange('0', '9');
return Integer.parseInt(matcher.retainFrom(fontShortName(font)));
}
private static String fontClass(PDFont font) {
CharMatcher matcher = CharMatcher.inRange('A', 'Z');
return (matcher.retainFrom(fontShortName(font))).toLowerCase();
}
private String textToTeX(String shortFontName, int code) throws JSONException {
JSONObject info = db.getInfo(shortFontName, code);
return info.getString("value");
}
public String fullTextToTeX(PDFont font, int code, float newEndX, float newY, float newEndY){
String shortFontName = fontClass(font);
try {
JSONObject info = db.getInfo(shortFontName, code);
String teXCode = info.getString("value");
StringBuilder preamble1 = new StringBuilder("");
StringBuilder preamble2 = new StringBuilder("");
StringBuilder postamble = new StringBuilder("");
boolean text = info.getBoolean("text");
boolean math = info.getBoolean("math");
boolean tacc = info.getBoolean("tacc");
boolean macc = info.getBoolean("macc");
String newFont = info.getString("font");
int newHeight = fontHeight(font);
//Font change, rm is seen as having no font
if (!newFont.equals(fs)) {
if (!fs.equals("rm"))
preamble1.insert(0, '}');
if (!newFont.equals("rm")) {
preamble2.append('\');
preamble2.append(newFont);
preamble2.append('{');
}
preamble1.insert(0, " fs = " + fs + " nFs = " + newFont + "\n");
fs = newFont;
}
if (height == 0) {
//preamble2.append(" Meow! am = " + accentMode + " fs = " + fs + " mm = " + mathMode + "\n");
}
//Subscripts/Superscripts
if (height > newHeight && newEndX > endX) {//New subscript/superscript
if (newEndY < endY) {//New superscript
//ssstatus.push(SSStatus.SUP);
preamble2.insert(0, "^{");
}
else if (newY > Y) {//New subscript
//ssstatus.push(SSStatus.SUB);
preamble2.insert(0, "_{");
}
//else {
// System.out.println("Please investigate the situation: texcode = " + teXCode + "endY = " + endY + " Y=" + Y + " endX=" + endX + " newEndY=" + newEndY + " newY=" + newY + " newEndX= " + newEndX);
//}
}
else if (height < newHeight && height != 0) {
//ssstatus.pop();
preamble1.append('}');
}
height = newHeight;
endX = newEndX;
endY = newEndY;
Y = newY;
//Enter or leave math mode
if (mathMode && !math && !macc) {
mathMode = false;
preamble1.append('$');
}
else if (!mathMode && !text && !tacc) {
mathMode = true;
preamble2.insert(0,'$');
}
//Accents
if (accentMode) {//If accent mode is ever entered we need to leave it at once
postamble.append('}');
accentMode = false;
}
if ((mathMode && macc) || (!mathMode && tacc)) {//Right now assume that anything that can be an accent is an accent
postamble.append('{');
if (mathMode)
teXCode = maccDict.get(teXCode);
accentMode = true;
}
if (teXCode.charAt(0) == '\')
return preamble1.toString() + preamble2.toString() + teXCode + ' ' + postamble.toString();
else
return preamble1.toString() + preamble2.toString() + teXCode + postamble.toString();
}
catch(JSONException e) {
return "\" + shortFontName + "{" + code + "}";
}
}
}
这里是主要内容class。
import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.font.PDFont;
import org.apache.pdfbox.text.PDFTextStripper;
import org.apache.pdfbox.text.TextPosition;
import com.google.common.base.CharMatcher;
import org.json.*;
import java.io.File;
import java.io.IOException;
import java.util.List;
import java.util.Stack;
public class TEX2TXT {
public static void main(String args[]) throws IOException {
TeXUtil util = new TeXUtil();
//Loading an existing document
File file = new File("/Users/CatLover/Documents/Tex/Examples/c4.pdf");
PDDocument document = PDDocument.load(file);
//Instantiate PDFTextStripper class
PDFTextStripper pdfStripper = new PDFTextStripper() {
protected void writeString(String text, List<TextPosition> textPositions) throws IOException {
TeXUtil util = new TeXUtil();
StringBuilder builder = new StringBuilder();
for(TextPosition position: textPositions) {
float Y = position.getY();
float endY = position.getEndY();
float endX = position.getEndX();
PDFont font = position.getFont();
int[] codes = position.getCharacterCodes();
for(int code: codes) {
builder.append(util.fullTextToTeX(font, code, endX, Y, endY));
}
}
writeString(builder.toString());
}
};
//Retrieving text from PDF document
String text = pdfStripper.getText(document);
System.out.println(text);
//Closing the document
document.close();
}
真正奇怪的是，TeXUtil 是在每次单词之间出现白色 space 时构造的，而 TeXUtil() 应该只调用一次。我不确定为什么会这样。由于 PDF 是由 LaTeX 生成的，而 LaTeX 不会在 PDF 中放置白色 space 字符，而是在字符之间留下 space 以隐式表示白色 space，这可能会影响 PDFBox 的工作方式。
您正在 PDFTextStripper 子类的 writeString 方法的第一行中构造一个新的 TeXUtil。如果您只是删除该行，它应该仍然可以引用您的 main 方法中定义的 util （尽管根据您使用的 java 的版本，您可能必须将其设为 final).