Wie verwende ich einen anderen Servlets-Service in einem anderen Servlet?

Question

Ich muß vorwärts/Handwerk Anforderung an einem anderen Servlet von anderen manuellen Service-Methode des Servlets. Dieses Servlet, das ein anderes Servlet aufruft, sollte die Daten aus der Antwort eines anderen Servlets extrahieren und eine eigene Antwort an den Client senden. Wie erreicht man diese Art von Funktionalität?

Client <-----> Servlet1 <-----> Servlet2

Ich weiß, es schlechtes Design ist, aber aufgrund der Umstände haben wir die Funktionalität von Servlet2 zu Servlet1

Answer 1

Sie HttpServletResponseWrapper verwenden müssen einzuführen und seine getOutputStream Methode außer Kraft setzen.

CustomHttpServletResponseWrapper und CustomServletOutputStream sind Implementierung für diese.

import java.io.IOException; 
import java.io.OutputStreamWriter; 
import java.io.PrintWriter; 

import javax.servlet.ServletOutputStream; 
import javax.servlet.http.HttpServletResponse; 
import javax.servlet.http.HttpServletResponseWrapper; 

public class CustomHttpServletResponseWrapper extends HttpServletResponseWrapper { 
    private ServletOutputStream outputStream; 
    private PrintWriter writer; 
    private CustomServletOutputStream os; 

    public CustomHttpServletResponseWrapper(HttpServletResponse response) throws IOException { 
     super(response); 
    } 

    @Override 
    public ServletOutputStream getOutputStream() throws IOException { 
     if (writer != null) { 
      throw new IllegalStateException("getWriter() has already been called on this response."); 
     } 

     if (outputStream == null) { 
      outputStream = getResponse().getOutputStream(); 
      os = new CustomServletOutputStream(outputStream); 
     } 

     return os; 
    } 

    @Override 
    public PrintWriter getWriter() throws IOException { 
     if (outputStream != null) { 
      throw new IllegalStateException("getOutputStream() has already been called on this response."); 
     } 

     if (writer == null) { 
      os = new CustomServletOutputStream(getResponse().getOutputStream()); 
      writer = new PrintWriter(new OutputStreamWriter(os, getResponse().getCharacterEncoding()), true); 
     } 

     return writer; 
    } 

    @Override 
    public void flushBuffer() throws IOException { 
     if (writer != null) { 
      writer.flush(); 
     } else if (outputStream != null) { 
      os.flush(); 
     } 
    } 

    public byte[] getContent() { 
     if (os != null) { 
      return os.getContent(); 
     } else { 
      return new byte[0]; 
     } 
    } 

} 

customServletOutputStream.java

import java.io.ByteArrayOutputStream; 
import java.io.IOException; 
import java.io.OutputStream; 

import javax.servlet.ServletOutputStream; 
import javax.servlet.WriteListener; 

public class CustomServletOutputStream extends ServletOutputStream { 

     private OutputStream outputStream; 
     private ByteArrayOutputStream content; 

     public CustomServletOutputStream(OutputStream outputStream) { 
      this.outputStream = outputStream; 
      this.content = new ByteArrayOutputStream(1024); 
     } 

     @Override 
     public void write(int b) throws IOException { 
      outputStream.write(b); 
      content.write(b); 
     } 

     public byte[] getContent() { 
      return content.toByteArray(); 

} 

     @Override 
     public boolean isReady() { 
      // TODO Auto-generated method stub 
      return false; 
     } 

     @Override 
     public void setWriteListener(WriteListener writeListener) { 
      // TODO Auto-generated method stub 

     } 
} 

Ihre Hauptklasse: Verwendung RequestDespetcher.include() Anfrage s2 zu umleiten und CustomHttpServletResponseWrapper passieren.

@ResponseBody 
    @RequestMapping("/s1")  
public String s1(HttpServletRequest req, HttpServletResponse res) throws Exception{ 
     RequestDispatcher rd = req.getRequestDispatcher("/oauth2/s2"); 
     CustomHttpServletResponseWrapper wrappedResponse = new CustomHttpServletResponseWrapper(res); 
     rd.include(req, wrappedResponse); 
     wrappedResponse.flushBuffer(); 
     byte[] result = wrappedResponse.getContent(); 
     System.out.println("result of servlet 2 "+new String(result)); 
    // here you got the result of servlet 2. manipulate it as you want. 

     return new String(result); 
    } 

    @ResponseBody 
    @RequestMapping("/s2") 
    public String s2(HttpServletRequest req, HttpServletResponse res){ 
     return "hello from s2"; 
    }