获取错误：无法访问FileNotFoundException得catch块.此异常从不从try语句主体引发

Question

我写了一段代码，每当我用特定的图像名称点击url时返回图像，如果找不到图像，就返回错误图像。

@GET
@Path("/getImage/{param1}")
@Produces({ "image/png", "image/jpeg", "image/gif", "image/jpg" })
public Response getProductimage(@PathParam("param1") String recievedData) {


    File file = null;
    try {
        file = new File("C:/Users/Gaurav/Desktop/AppData/"
                + recievedData);

    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        file = new File("C:/Users/Gaurav/Desktop/AppData/error.png");

        System.out.println(e.getMessage());
    }

    return Response.ok(file).build();

}

但我还是会遇到这个错误，当我试图击中错误的图像

SEVERE: Servlet.service() for servlet [Jersey RESTful Application] in context with path [/WebServices] threw exception [org.glassfish.jersey.server.ContainerException: java.io.FileNotFoundException: C:\Users\Gaurav\Desktop\AppData\average11.png (The system cannot find the file specified)] with root cause
java.io.FileNotFoundException: C:\Users\Gaurav\Desktop\AppData\average.png15 (The system cannot find the file specified)
    at java.io.FileInputStream.open(Native Method)
    at java.io.FileInputStream.<init>(FileInputStream.java:131)
    at org.glassfish.jersey.message.internal.FileProvider.writeTo(FileProvider.java:115)

代码出了什么问题？

Answer 1

调用新文件（“x:/non/existing/File”）不会引发任何异常，因此您的catch块永远不会被执行。

您应该使用.exists()来检查文件是否存在，或者使用.CanRead()来检查您是否真的可以读取它。

File file = new File("C:/Users/Gaurav/Desktop/AppData", recievedData);
if (!file.canRead()) {
    file = new File("C:/Users/Gaurav/Desktop/AppData/error.png");
}
return Response.ok(file).build();