Question

我有以下方法：

public String readJson(){
    String everything = "";
    try(BufferedReader br = new BufferedReader(new FileReader("/users/mypc/test/etc/one.json"))) {
        StringBuilder sb = new StringBuilder();
        String line = br.readLine();

        while (line != null) {
            sb.append(line);
            sb.append(System.lineSeparator());
            line = br.readLine();
        }
        everything = sb.toString();
        logger.debug("Everything: " + everything);
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    logger.debug("line: " + everything);
    return everything;
}

这样可以正常工作。我的问题是我不想硬编码文件路径/users/mypc/test/etc/one.json。我尝试通过执行以下操作将其添加到属性文件中：

test.properties：

file1=/users/mypc/test/etc/one.json

PropertiesHelper.java：

public String GET_FILE_ONE = "file1";

private static String one;

public String getJsonFile(){
    one = config.getProperty(this.GET_FILE_ONE);
    return one;
}

JsonReader.java：

private static PropertiesHelper helper;

final String GET_FILE_ONE = helper.getJsonFile();

public String readJson(){
String everything = "";
try(BufferedReader br = new BufferedReader(new FileReader(GET_FILE_ONE))) {
    StringBuilder sb = new StringBuilder();
    String line = br.readLine();

    while (line != null) {
        sb.append(line);
        sb.append(System.lineSeparator());
        line = br.readLine();
    }
    everything = sb.toString();
    logger.debug("Everything: " + everything);
} catch (FileNotFoundException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}
logger.debug("line: " + everything);
return everything;
}

我过去做过类似的事情，但这次我得到一个NullPointerException。我一直在盯着这一段时间，看不出有什么不对。我在属性文件中设置文件路径的方式有什么问题，还是有其他我错过的东西？

Answer 1

Donnacha在上面回答。

通过添加私有静态PropertiesHelper helper = new PropertiesHelper（）;解决了该问题。到JsonReader.java。见下文：

private static PropertiesHelper helper;

private static PropertiesHelper helper = new PropertiesHelper();

final String GET_FILE_ONE = helper.getJsonFile();

public String readJson(){
    String everything = "";
    try(BufferedReader br = new BufferedReader(new FileReader(GET_FILE_ONE))) {
        StringBuilder sb = new StringBuilder();
        String line = br.readLine();

        while (line != null) {
            sb.append(line);
            sb.append(System.lineSeparator());
            line = br.readLine();
        }
        everything = sb.toString();
        logger.debug("Everything: " + everything);
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    logger.debug("line: " + everything);
    return everything;
}

引用属性文件时出现NullPointerException

1 个答案: