Reading files from relative paths on Tomcat

Question

I need to run a web-app on Tomcat, but it cannot read the txt files(from a relative paths as below) on Tomcat. However, it does work if I use a full path.

So I am wondering where can I put these txt files so that when Tomcat started, the app can successfully read the txt files from a relative path.

Currently, the project structure is as follows, the txt files is located on the same directory as src file in Project Explorer in Eclipse .

Project_Name
src
   java files

EDGES.txt
NODES.txt

The code is as follows, I am appreciated if someone can give me an answer in details, since I am quite new to Java.

The code is as follows:

public class RouteingDao {
    NodeJSONReader nodeInput = new NodeJSONReader("NODES.txt");
    EdgeJSONReader edgeInput = new EdgeJSONReader("EDGES.txt");
    ...
}

The NodeJSONReader/EdgeJSONReader class is as follows:

public class EdgeJSONReader {
    private EdgeEntity[] edgeEntity;

    // constructor
    public EdgeJSONReader(String JSON_FILE) {
        edgeEntity = readEntityFromFile(JSON_FILE);
    }

    // load the JSON data from local file 
    public EdgeEntity[] readEntityFromFile(String JSON_FILE) {
        try {
            Reader reader = new FileReader(JSON_FILE);
            Gson gson = new Gson();
            edgeEntity = gson.fromJson(reader, EdgeEntity[].class);
        } 
        ...
    }
}

Answer 1

If you are using a servlet, then access the servlet context and the getRealPath method.

this.getServletContext().getRealPath("WEB-INF/nodes.txt")

The relative path sent to getRealPath will be expanded to the location of the files for your web app. You can add any path you like, even to a hidden file in WEB-INF.

From a JSP you can use

${pageContext.servletContext.getRealPath("WEB-INF/nodes.txt")}

Be careful, this will be in the build directory, so any changes to nodes.txt will not be saved to the original file.