假设我正在一个非常大的项目中工作，并且注意到有一个空的打印行，所以我假设有一个System.out.println（"）；位于代码中的某个位置。除了在整个项目中搜索所有出现的System.out.println之外，我该如何尝试弄清楚它在哪里？
如果您使用的是Java 8+，Durian有一个StackDumper类，它可以很容易地找到打印给定行的位置：
StackDumper.dumpWhenSysOutContains("SomeTrigger")
当打印"SomeTrigger"时，它将被转储到System.err:
+----------
| Triggered by SomeTrigger
| at package.MyClass.myMethod(MyClass.java:62)
| (the rest of the stacktrace)
+----------/
对于您的情况（查找空字符串），它有点复杂：
PrintStream sysOutClean = System.out;
StringPrinter sysOutReplacement = new StringPrinter(StringPrinter.stringsToLines(line -> {
if (line.isEmpty()) {
StackDumper.dump("Found empty line");
}
sysOutClean.println(line);
}));
System.setOut(sysOutReplacement.toPrintStream());
现在，如果有这样的东西：
System.out.println("ABC");
System.out.println("123");
System.out.println("");
System.out.println("DEF");
然后你的控制台会像这样：
ABC
123
+----------
| Found empty line
| at package.MyClass.myMethod(MyClass.java:62)
| (the rest of the stacktrace)
+----------/
DEF
您可以实现自己的PrintStream，并使用System.setOut来替换默认的stdout。然后在类中放置调试标记（如果打印了空字符串），或者通过调用堆栈打印出方法名称（抛出并捕获异常并获取堆栈信息）。
示例：
/** Control sysout prints */
public static void main(String[] arg) throws Exception {
System.out.println("Default"); //print normally
SysOutController.setSysOutLocationAddressor();
System.out.println("With Address"); //prints with calling location, and on click location cursor directly focus when System.out.**() called
SysOutController.ignoreSysout();
System.out.println("Ignored"); //this line will never prints
SysOutController.resetSysOut();
System.out.println("Default"); //print normally as it is (reset)
}
只需调用以下类的方法，即可帮助开发人员控制sysout
import java.io.FileDescriptor;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;
/**
* Class which controls System.out prints in console <br/>
* this class will helps developers to control prints in console
* @implSpec
* <pre><code>
* System.out.println("Default"); //print normally
*
* SysOutController.setSysOutLocationAddressor();
* System.out.println("With Address"); //prints with calling location
*
* SysOutController.ignoreSysout();
* System.out.println("Ignored"); //this line will never prints
*
* SysOutController.resetSysOut();
* System.out.println("Default"); //print normally as it is (reset)
* </code></pre>
* @author Dharmendrasinh Chudasama
*/
public class SysOutController {
private static void setOut(OutputStream out){
System.setOut(new PrintStream(out));
}
private static final OutputStream CONSOLE = new FileOutputStream(FileDescriptor.out);
/**
* Reset System.out.print* method
* @author Dharmendrasinh Chudasama
*/
public static void resetSysOut() { setOut(CONSOLE); }
/**
* System.out.print* will not print anything in console
* @author Dharmendrasinh Chudasama
*/
public static void ignoreSysout() {
setOut(new OutputStream() {
@Override public void write(int b) throws IOException {}
});
}
/**
* Address/location of calling System.out.* method will append in console
* @author Dharmendrasinh Chudasama
*/
public static void setSysOutLocationAddressor() {
setOut(new OutputStream() {
@Override
public void write(int b) throws IOException {
if(b=='n'){ //if newLine
final StackTraceElement callerStEl = new Throwable().getStackTrace()[9];
String pathData =
"u001B[37m" //low-visibality
+ "t :: ("+callerStEl.getFileName()+":"+callerStEl.getLineNumber()+") ["+callerStEl+"]" //code path
+ "u001B[0m "; //reset
CONSOLE.write(pathData.getBytes());
}
CONSOLE.write(b);
}
});
}
}
这也可能是由于库的某些原因，如果你觉得这只是因为System.out.println，那么
解决方案1:下面的代码片段应该可以帮助您找到执行它的位置。
import java.io.FileNotFoundException;
import java.io.PrintStream;
public class CustomPrintStream extends PrintStream {
public CustomPrintStream(String fileName) throws FileNotFoundException {
super(fileName);
}
@Override
public void print(String s) {
try{
if(s == null || s.equals("")){
throw new Exception("Invalid print message");
}
super.print(s);
}catch(Exception e){
//TODO Change to your logger framework and leave it as same
e.printStackTrace();
}
}
public static void main(String[] args) {
try {
//TODO : Change to your favorite path and make sure mentioned
//file is available
CustomPrintStream customPrintStream = new CustomPrintStream
("/home/prem/Desktop/test.log");
System.setOut(customPrintStream);
System.out.println("");
} catch (FileNotFoundException e) {
//TODO Change to your logger framework and leave it as same
e.printStackTrace();
}
}
}
解决方案2:由于IDE是可用的，请从他们那里获得帮助。如果您正在使用eclipse菜单->搜索->文件搜索->放置系统.out.println（"）；在包含搜索和搜索它。
我宁愿说不要在任何代码中使用System.out.println，因为您可以使用checkstyle，并确信因此没有开发人员使用它们。
定义一个类NewPrintStream扩展PrintStream
import java.io.FileNotFoundException;
import java.io.PrintStream;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class NewPrintStream extends PrintStream {
private static final Logger LOGGER = LoggerFactory.getLogger(NewPrintStream.class);
public NewPrintStream(String fileName) throws FileNotFoundException {
super(fileName);
}
@Override
public void println(String x) {
LOGGER.info("xxxxxxx", new Exception("xxxx"));
}
}
然后在主类中设置stdout/stderr打印流
System.setOut(new NewPrintStream("aaa"));
System.setErr(new NewPrintStream("aaa"));
在PrintStream.println(String x)中放置一个条件断点，条件设置为x.equals("")或任何字符串。