在Spring Batch中解密后通过MultiResourceItemReader读取文件

Question

I'm developing a spring batch to read multiple files from a folder, process it and write the result in DB. I'm using MultiResourceItemReader to read files from the folder. but the files might be encrypted so , i need to decrypt the file before reading. What is the best way to do this?

1) Should I use a step before reading, processing and writing ? 2) Should I override doOpen from FlatFileItemReader which was set as delegate to MultiResourceItemReader ? 3) Should I override open in MultiResourceItemReader itself ?

I think, overriding an already existing method is not advisable, as we may end up in duplication or missing code. Please advise

Answer 1

I guess you are using a FlatFileItemReader as delegate here?

Then you could make it with a customized BufferedReaderFactory

Java Code ( not tested! i have no experience using Cipher )

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.io.UnsupportedEncodingException;

import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;
import javax.crypto.spec.IvParameterSpec;

import org.springframework.batch.item.file.BufferedReaderFactory;
import org.springframework.core.io.Resource;

public class EncryptedBufferedItemReaderFactory implements BufferedReaderFactory {

  private String keyFile;
  private String algorithm;

  @Override
  public BufferedReader create(final Resource resource, final String encoding) throws UnsupportedEncodingException, IOException {
    FileInputStream fis = new FileInputStream(resource.getFile());
    CipherInputStream cis = new CipherInputStream(fis, createCipher());
    return new BufferedReader(new InputStreamReader(cis, encoding));
  }

  private Cipher createCipher() throws IOException, FileNotFoundException {
    ObjectInputStream ois = new ObjectInputStream(new FileInputStream(keyFile));
    Cipher cipher;
    try {
      DESKeySpec ks = new DESKeySpec((byte[]) ois.readObject());
      SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");
      SecretKey key = skf.generateSecret(ks);
      cipher = Cipher.getInstance(algorithm);
      cipher.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec((byte[]) ois.readObject()));
    } catch (Exception ex) {
      throw new IOException(ex);
    } finally {
      ois.close();
    }
    return cipher;
  }

  public void setKeyFile(final String keyFile) {
    this.keyFile = keyFile;
  }

  public void setAlgorithm(final String algorithm) {
    this.algorithm = algorithm;
  }
}

for algorithm see Java standard algorithms

example bean configuration

<bean id="multiResourceItemReader" class="org.springframework.batch.item.file.MultiResourceItemReader" scope="step">
  <property name="resources" value="#{jobParameters['whateverYouChosen']}" />
  <property name="delegate" ref="flatFileItemReader" />
</bean>

<bean id="flatFileItemReader" class="org.springframework.batch.item.file.FlatFileItemReader" scope="step">
  <!-- some properties you already have, like lineMapper -->
  <property name="bufferedReaderFactory" ref ="encryptedBufferedReaderFactory" />
</bean>

<bean id="encryptedBufferedReaderFactory" class="your.com.package.EncryptedBufferedReaderFactory" scope="step">
  <property name="keyFile" value="#{jobParameters['pathToKeyFile']}" />
  <property name="algorithm" value="#{jobParameters['algorithm']}" />
</bean>