I want to develop with Servlets in Eclipse, but it says that the package javax.servlet
/ jakarta.servlet
cannot be resolved. How can I add javax.servlet
/ jakarta.servlet
package to my Eclipse project?
Java – How to import the javax.servlet / jakarta.servlet API in the Eclipse project
eclipsejavaservlets
Related Solutions
In the package explorer, in the upper right corner of the view, there is a little down arrow. Tool tip will say view menu. From that menu, select filters
From there, uncheck .* resources.
So Package Explorer -> View Menu -> Filters -> uncheck .* resources
.
With Eclipse Kepler and OS X this is a bit different:
Package Explorer -> Customize View -> Filters -> uncheck .* resources
Summarize other answers I found 11 main ways to do this (see below). And I wrote some performance tests (see results below):
Ways to convert an InputStream to a String:
Using
IOUtils.toString
(Apache Utils)String result = IOUtils.toString(inputStream, StandardCharsets.UTF_8);
Using
CharStreams
(Guava)String result = CharStreams.toString(new InputStreamReader( inputStream, Charsets.UTF_8));
Using
Scanner
(JDK)Scanner s = new Scanner(inputStream).useDelimiter("\\A"); String result = s.hasNext() ? s.next() : "";
Using Stream API (Java 8). Warning: This solution converts different line breaks (like
\r\n
) to\n
.String result = new BufferedReader(new InputStreamReader(inputStream)) .lines().collect(Collectors.joining("\n"));
Using parallel Stream API (Java 8). Warning: This solution converts different line breaks (like
\r\n
) to\n
.String result = new BufferedReader(new InputStreamReader(inputStream)) .lines().parallel().collect(Collectors.joining("\n"));
Using
InputStreamReader
andStringBuilder
(JDK)int bufferSize = 1024; char[] buffer = new char[bufferSize]; StringBuilder out = new StringBuilder(); Reader in = new InputStreamReader(stream, StandardCharsets.UTF_8); for (int numRead; (numRead = in.read(buffer, 0, buffer.length)) > 0; ) { out.append(buffer, 0, numRead); } return out.toString();
Using
StringWriter
andIOUtils.copy
(Apache Commons)StringWriter writer = new StringWriter(); IOUtils.copy(inputStream, writer, "UTF-8"); return writer.toString();
Using
ByteArrayOutputStream
andinputStream.read
(JDK)ByteArrayOutputStream result = new ByteArrayOutputStream(); byte[] buffer = new byte[1024]; for (int length; (length = inputStream.read(buffer)) != -1; ) { result.write(buffer, 0, length); } // StandardCharsets.UTF_8.name() > JDK 7 return result.toString("UTF-8");
Using
BufferedReader
(JDK). Warning: This solution converts different line breaks (like\n\r
) toline.separator
system property (for example, in Windows to "\r\n").String newLine = System.getProperty("line.separator"); BufferedReader reader = new BufferedReader( new InputStreamReader(inputStream)); StringBuilder result = new StringBuilder(); for (String line; (line = reader.readLine()) != null; ) { if (result.length() > 0) { result.append(newLine); } result.append(line); } return result.toString();
Using
BufferedInputStream
andByteArrayOutputStream
(JDK)BufferedInputStream bis = new BufferedInputStream(inputStream); ByteArrayOutputStream buf = new ByteArrayOutputStream(); for (int result = bis.read(); result != -1; result = bis.read()) { buf.write((byte) result); } // StandardCharsets.UTF_8.name() > JDK 7 return buf.toString("UTF-8");
Using
inputStream.read()
andStringBuilder
(JDK). Warning: This solution has problems with Unicode, for example with Russian text (works correctly only with non-Unicode text)StringBuilder sb = new StringBuilder(); for (int ch; (ch = inputStream.read()) != -1; ) { sb.append((char) ch); } return sb.toString();
Warning:
Solutions 4, 5 and 9 convert different line breaks to one.
Solution 11 can't work correctly with Unicode text
Performance tests
Performance tests for small String
(length = 175), url in github (mode = Average Time, system = Linux, score 1,343 is the best):
Benchmark Mode Cnt Score Error Units
8. ByteArrayOutputStream and read (JDK) avgt 10 1,343 ± 0,028 us/op
6. InputStreamReader and StringBuilder (JDK) avgt 10 6,980 ± 0,404 us/op
10. BufferedInputStream, ByteArrayOutputStream avgt 10 7,437 ± 0,735 us/op
11. InputStream.read() and StringBuilder (JDK) avgt 10 8,977 ± 0,328 us/op
7. StringWriter and IOUtils.copy (Apache) avgt 10 10,613 ± 0,599 us/op
1. IOUtils.toString (Apache Utils) avgt 10 10,605 ± 0,527 us/op
3. Scanner (JDK) avgt 10 12,083 ± 0,293 us/op
2. CharStreams (guava) avgt 10 12,999 ± 0,514 us/op
4. Stream Api (Java 8) avgt 10 15,811 ± 0,605 us/op
9. BufferedReader (JDK) avgt 10 16,038 ± 0,711 us/op
5. parallel Stream Api (Java 8) avgt 10 21,544 ± 0,583 us/op
Performance tests for big String
(length = 50100), url in github (mode = Average Time, system = Linux, score 200,715 is the best):
Benchmark Mode Cnt Score Error Units
8. ByteArrayOutputStream and read (JDK) avgt 10 200,715 ± 18,103 us/op
1. IOUtils.toString (Apache Utils) avgt 10 300,019 ± 8,751 us/op
6. InputStreamReader and StringBuilder (JDK) avgt 10 347,616 ± 130,348 us/op
7. StringWriter and IOUtils.copy (Apache) avgt 10 352,791 ± 105,337 us/op
2. CharStreams (guava) avgt 10 420,137 ± 59,877 us/op
9. BufferedReader (JDK) avgt 10 632,028 ± 17,002 us/op
5. parallel Stream Api (Java 8) avgt 10 662,999 ± 46,199 us/op
4. Stream Api (Java 8) avgt 10 701,269 ± 82,296 us/op
10. BufferedInputStream, ByteArrayOutputStream avgt 10 740,837 ± 5,613 us/op
3. Scanner (JDK) avgt 10 751,417 ± 62,026 us/op
11. InputStream.read() and StringBuilder (JDK) avgt 10 2919,350 ± 1101,942 us/op
Graphs (performance tests depending on Input Stream length in Windows 7 system)
Performance test (Average Time) depending on Input Stream length in Windows 7 system:
length 182 546 1092 3276 9828 29484 58968
test8 0.38 0.938 1.868 4.448 13.412 36.459 72.708
test4 2.362 3.609 5.573 12.769 40.74 81.415 159.864
test5 3.881 5.075 6.904 14.123 50.258 129.937 166.162
test9 2.237 3.493 5.422 11.977 45.98 89.336 177.39
test6 1.261 2.12 4.38 10.698 31.821 86.106 186.636
test7 1.601 2.391 3.646 8.367 38.196 110.221 211.016
test1 1.529 2.381 3.527 8.411 40.551 105.16 212.573
test3 3.035 3.934 8.606 20.858 61.571 118.744 235.428
test2 3.136 6.238 10.508 33.48 43.532 118.044 239.481
test10 1.593 4.736 7.527 20.557 59.856 162.907 323.147
test11 3.913 11.506 23.26 68.644 207.591 600.444 1211.545
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Best Answer
Ensure you've the right Eclipse and Server version
Ensure that you're using at least Eclipse IDE for Enterprise Java developers (with the Enterprise). It contains development tools to create dynamic web projects and easily integrate servletcontainers (those tools are part of Web Tools Platform, WTP). In case you already had Eclipse IDE for Java (without Enterprise), and manually installed some related plugins, then chances are that it wasn't done properly. You'd best trash it and grab the real Eclipse IDE for Enterprise Java one.
You also need to ensure that you already have a servletcontainer installed on your machine which implements at least the same Servlet API version as the servletcontainer in the production environment, for example Apache Tomcat, Oracle GlassFish, JBoss AS/WildFly, etc. Usually, just downloading the ZIP file and extracting it is sufficient. In case of Tomcat, do not download the EXE format, that's only for Windows based production environments. See also a.o. Several ports (8005, 8080, 8009) required by Tomcat Server at localhost are already in use.
A servletcontainer is a concrete implementation of the Servlet API. Note that the Java EE SDK download at Oracle.com basically contains GlassFish. So if you happen to already have downloaded Java EE SDK, then you basically already have GlassFish. Also note that for example GlassFish and JBoss AS/WildFly are more than just a servletcontainer, they also supports JSF, EJB, JPA and all other Java EE fanciness. See also a.o. What exactly is Java EE?
Ensure that you're using the right Servlet package
The
javax.*
package has been renamed tojakarta.*
package since Servlet API version 5.0 which is part of Jakarta EE 9 (Tomcat 10, TomEE 9, WildFly 22 Preview, GlassFish 6, Payara 6, Liberty 22, etc). So if you're targeting these server versions or newer, then you need to replaceby
in order to get it to compile, else you might risk to face this build error
Integrate Server in Eclipse and associate it with Project
Once having installed both Eclipse for Enterprise Java and a servletcontainer on your machine, do the following steps in Eclipse:
Integrate servletcontainer in Eclipse
a. Via Servers view
Open the Servers view in the bottom box.
Rightclick there and choose New > Server.
Pick the appropriate servletcontainer make and version and walk through the wizard.
b. Or, via Eclipse preferences
Open Window > Preferences > Server > Runtime Environments.
You can Add, Edit and Remove servers here.
Associate server with project
a. In new project
Open the Project Navigator/Explorer on the left hand side.
Rightclick there and choose New > Project and then in menu Web > Dynamic Web Project.
In the wizard, set the Target Runtime to the integrated server.
b. Or, in existing project
Rightclick project and choose Properties.
In Targeted Runtimes section, select the integrated server.
Either way, Eclipse will then automatically take the servletcontainer's libraries in the build path. This way you'll be able to import and use the Servlet API.
Never carry around loose server-specific JAR files
You should in any case not have the need to fiddle around in the Build Path property of the project. You should above all never manually copy/download/move/include the individual servletcontainer-specific libraries like
servlet-api.jar
,jsp-api.jar
,el-api.jar
,j2ee.jar
,javaee.jar
, etc. It would only lead to future portability, compatibility, classpath and maintainability troubles, because your webapp would not work when it's deployed to a servletcontainer of a different make/version than where those libraries are originally obtained from.In case you're using Maven, you need to make absolutely sure that servletcontainer-specific libraries which are already provided by the target runtime are marked as
<scope>provided</scope>
. You can find examples of properpom.xml
dependency declarations for Tomcat 10+, Tomcat 9-, JEE 9+ and JEE 8- in this answer: Tomcat 9 casting servlets to javax.servlet.Servlet instead of jakarta.servlet.http.HttpServletHere are some typical exceptions which you can get when you litter the
/WEB-INF/lib
or even/JRE/lib
,/JRE/lib/ext
, etc with servletcontainer-specific libraries in a careless attempt to fix the compilation errors: