Servlet源码

顶级接口:Servlet:

package javax.servlet;


import java.io.IOException;




public interface Servlet {


   
    public void init(ServletConfig config) throws ServletException;
    
    public ServletConfig getServletConfig();
    
    public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException;

    public String getServletInfo();

    public void destroy();
}

GenericServlet抽象类:

package javax.servlet;


import java.io.IOException;
import java.util.Enumeration;


public abstract class GenericServlet implements Servlet, ServletConfig,
        java.io.Serializable {


    private static final long serialVersionUID = 1L;


    private transient ServletConfig config;
    
    @Override
    public void init(ServletConfig config) throws ServletException {
        this.config = config;
        this.init();
    }
    
    public void init() throws ServletException {
        // NOOP by default
    }
    
    @Override
    public abstract void service(ServletRequest req, ServletResponse res) throws ServletException, IOException;
    
    @Override
    public ServletConfig getServletConfig() {
        return config;
    }
    
    @Override
    public String getServletInfo() {
        return "";
    } 
   
    @Override
    public void destroy() {
        // NOOP by default
    }
    
    
    public GenericServlet() {
        // NOOP
    }
    @Override
    public String getInitParameter(String name) {
        return getServletConfig().getInitParameter(name);
    }
    @Override
    public Enumeration<String> getInitParameterNames() {
        return getServletConfig().getInitParameterNames();
    }
    public void log(String msg) {
        getServletContext().log(getServletName() + ": " + msg);
    }
    public void log(String message, Throwable t) {
        getServletContext().log(getServletName() + ": " + message, t);
    }
    @Override
    public String getServletName() {
        return config.getServletName();
    }
    @Override
    public ServletContext getServletContext() {
        return getServletConfig().getServletContext();
    }
}

HttpServlet:

package javax.servlet.http;


import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.Method;
import java.text.MessageFormat;
import java.util.Enumeration;
import java.util.ResourceBundle;
import javax.servlet.DispatcherType;
import javax.servlet.GenericServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;


public abstract class HttpServlet extends GenericServlet {


    private static final long serialVersionUID = 1L;
    private static final String METHOD_DELETE = "DELETE";
    private static final String METHOD_HEAD = "HEAD";
    private static final String METHOD_GET = "GET";
    private static final String METHOD_OPTIONS = "OPTIONS";
    private static final String METHOD_POST = "POST";
    private static final String METHOD_PUT = "PUT";
    private static final String METHOD_TRACE = "TRACE";
    private static final String HEADER_IFMODSINCE = "If-Modified-Since";
    private static final String HEADER_LASTMOD = "Last-Modified";
    private static final String LSTRING_FILE =
        "javax.servlet.http.LocalStrings";
    private static ResourceBundle lStrings =
        ResourceBundle.getBundle(LSTRING_FILE);
    
    public HttpServlet() {
        // NOOP
    }
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException
    {
        String protocol = req.getProtocol();
        String msg = lStrings.getString("http.method_get_not_supported");
        if (protocol.endsWith("1.1")) {
            resp.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, msg);
        } else {
            resp.sendError(HttpServletResponse.SC_BAD_REQUEST, msg);
        }
    }
    protected long getLastModified(HttpServletRequest req) {
        return -1;
    }
    protected void doHead(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {


        if (DispatcherType.INCLUDE.equals(req.getDispatcherType())) {
            doGet(req, resp);
        } else {
            NoBodyResponse response = new NoBodyResponse(resp);
            doGet(req, response);
            response.setContentLength();
        }
    }
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {


        String protocol = req.getProtocol();
        String msg = lStrings.getString("http.method_post_not_supported");
        if (protocol.endsWith("1.1")) {
            resp.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, msg);
        } else {
            resp.sendError(HttpServletResponse.SC_BAD_REQUEST, msg);
        }
    }
    protected void doPut(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {


        String protocol = req.getProtocol();
        String msg = lStrings.getString("http.method_put_not_supported");
        if (protocol.endsWith("1.1")) {
            resp.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, msg);
        } else {
            resp.sendError(HttpServletResponse.SC_BAD_REQUEST, msg);
        }
    }
    protected void doDelete(HttpServletRequest req,
                            HttpServletResponse resp)
        throws ServletException, IOException {


        String protocol = req.getProtocol();
        String msg = lStrings.getString("http.method_delete_not_supported");
        if (protocol.endsWith("1.1")) {
            resp.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, msg);
        } else {
            resp.sendError(HttpServletResponse.SC_BAD_REQUEST, msg);
        }
    }
    private static Method[] getAllDeclaredMethods(Class<?> c) {


        if (c.equals(javax.servlet.http.HttpServlet.class)) {
            return null;
        }
        Method[] parentMethods = getAllDeclaredMethods(c.getSuperclass());
        Method[] thisMethods = c.getDeclaredMethods();


        if ((parentMethods != null) && (parentMethods.length > 0)) {
            Method[] allMethods =
                new Method[parentMethods.length + thisMethods.length];
            System.arraycopy(parentMethods, 0, allMethods, 0,
                             parentMethods.length);
            System.arraycopy(thisMethods, 0, allMethods, parentMethods.length,
                             thisMethods.length);


            thisMethods = allMethods;
        }


        return thisMethods;
    }
    protected void doOptions(HttpServletRequest req,
            HttpServletResponse resp)
        throws ServletException, IOException {


        Method[] methods = getAllDeclaredMethods(this.getClass());


        boolean ALLOW_GET = false;
        boolean ALLOW_HEAD = false;
        boolean ALLOW_POST = false;
        boolean ALLOW_PUT = false;
        boolean ALLOW_DELETE = false;
        boolean ALLOW_TRACE = true;
        boolean ALLOW_OPTIONS = true;
        for (int i=0; i<methods.length; i++) {
            Method m = methods[i];


            if (m.getName().equals("doGet")) {
                ALLOW_GET = true;
                ALLOW_HEAD = true;
            }
            if (m.getName().equals("doPost"))
                ALLOW_POST = true;
            if (m.getName().equals("doPut"))
                ALLOW_PUT = true;
            if (m.getName().equals("doDelete"))
                ALLOW_DELETE = true;
        }


        String allow = null;
        if (ALLOW_GET)
            allow=METHOD_GET;
        if (ALLOW_HEAD)
            if (allow==null) allow=METHOD_HEAD;
            else allow += ", " + METHOD_HEAD;
        if (ALLOW_POST)
            if (allow==null) allow=METHOD_POST;
            else allow += ", " + METHOD_POST;
        if (ALLOW_PUT)
            if (allow==null) allow=METHOD_PUT;
            else allow += ", " + METHOD_PUT;
        if (ALLOW_DELETE)
            if (allow==null) allow=METHOD_DELETE;
            else allow += ", " + METHOD_DELETE;
        if (ALLOW_TRACE)
            if (allow==null) allow=METHOD_TRACE;
            else allow += ", " + METHOD_TRACE;
        if (ALLOW_OPTIONS)
            if (allow==null) allow=METHOD_OPTIONS;
            else allow += ", " + METHOD_OPTIONS;


        resp.setHeader("Allow", allow);
    }
    protected void doTrace(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException
    {
        int responseLength;


        String CRLF = "\r\n";
        StringBuilder buffer = new StringBuilder("TRACE ").append(req.getRequestURI())
            .append(" ").append(req.getProtocol());


        Enumeration<String> reqHeaderEnum = req.getHeaderNames();


        while( reqHeaderEnum.hasMoreElements() ) {
            String headerName = reqHeaderEnum.nextElement();
            buffer.append(CRLF).append(headerName).append(": ")
                .append(req.getHeader(headerName));
        }
        buffer.append(CRLF);


        responseLength = buffer.length();


        resp.setContentType("message/http");
        resp.setContentLength(responseLength);
        ServletOutputStream out = resp.getOutputStream();
        out.print(buffer.toString());
        out.close();
        return;
    }
    protected void service(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {


        String method = req.getMethod();


        if (method.equals(METHOD_GET)) {
            long lastModified = getLastModified(req);
            if (lastModified == -1) {
                doGet(req, resp);
            } else {
                long ifModifiedSince;
                try {
                    ifModifiedSince = req.getDateHeader(HEADER_IFMODSINCE);
                } catch (IllegalArgumentException iae) {
                    ifModifiedSince = -1;
                }
                if (ifModifiedSince < (lastModified / 1000 * 1000)) {
                    maybeSetLastModified(resp, lastModified);
                    doGet(req, resp);
                } else {
                    resp.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
                }
            }


        } else if (method.equals(METHOD_HEAD)) {
            long lastModified = getLastModified(req);
            maybeSetLastModified(resp, lastModified);
            doHead(req, resp);


        } else if (method.equals(METHOD_POST)) {
            doPost(req, resp);


        } else if (method.equals(METHOD_PUT)) {
            doPut(req, resp);


        } else if (method.equals(METHOD_DELETE)) {
            doDelete(req, resp);


        } else if (method.equals(METHOD_OPTIONS)) {
            doOptions(req,resp);


        } else if (method.equals(METHOD_TRACE)) {
            doTrace(req,resp);


        } else {
   
            String errMsg = lStrings.getString("http.method_not_implemented");
            Object[] errArgs = new Object[1];
            errArgs[0] = method;
            errMsg = MessageFormat.format(errMsg, errArgs);


            resp.sendError(HttpServletResponse.SC_NOT_IMPLEMENTED, errMsg);
        }
    }
    private void maybeSetLastModified(HttpServletResponse resp,
                                      long lastModified) {
        if (resp.containsHeader(HEADER_LASTMOD))
            return;
        if (lastModified >= 0)
            resp.setDateHeader(HEADER_LASTMOD, lastModified);
    }
    @Override
    public void service(ServletRequest req, ServletResponse res)
        throws ServletException, IOException {


        HttpServletRequest  request;
        HttpServletResponse response;


        try {
            request = (HttpServletRequest) req;
            response = (HttpServletResponse) res;
        } catch (ClassCastException e) {
            throw new ServletException("non-HTTP request or response");
        }
        service(request, response);
    }
}
class NoBodyResponse extends HttpServletResponseWrapper {
    private NoBodyOutputStream                noBody;
    private PrintWriter                        writer;
    private boolean                        didSetContentLength;


   
    NoBodyResponse(HttpServletResponse r) {
        super(r);
        noBody = new NoBodyOutputStream();
    }
    void setContentLength() {
        if (!didSetContentLength) {
            if (writer != null) {
                writer.flush();
            }
            super.setContentLength(noBody.getContentLength());
        }
    }
    @Override
    public void setContentLength(int len) {
        super.setContentLength(len);
        didSetContentLength = true;
    }
    @Override
    public void setHeader(String name, String value) {
        super.setHeader(name, value);
        checkHeader(name);
    }
    @Override
    public void addHeader(String name, String value) {
        super.addHeader(name, value);
        checkHeader(name);
    }
    @Override
    public void setIntHeader(String name, int value) {
        super.setIntHeader(name, value);
        checkHeader(name);
    }
    @Override
    public void addIntHeader(String name, int value) {
        super.addIntHeader(name, value);
        checkHeader(name);
    }
    private void checkHeader(String name) {
        if ("content-length".equalsIgnoreCase(name)) {
            didSetContentLength = true;
        }
    }
    @Override
    public ServletOutputStream getOutputStream() throws IOException {
        return noBody;
    }
    @Override
    public PrintWriter getWriter() throws UnsupportedEncodingException {


        if (writer == null) {
            OutputStreamWriter w;


            w = new OutputStreamWriter(noBody, getCharacterEncoding());
            writer = new PrintWriter(w);
        }
        return writer;
    }
}
class NoBodyOutputStream extends ServletOutputStream {


    private static final String LSTRING_FILE =
        "javax.servlet.http.LocalStrings";
    private static ResourceBundle lStrings =
        ResourceBundle.getBundle(LSTRING_FILE);


    private int                contentLength = 0;
    NoBodyOutputStream() {
      
    }
    int getContentLength() {
        return contentLength;
    }
    @Override
    public void write(int b) {
        contentLength++;
    }
    @Override
    public void write(byte buf[], int offset, int len) throws IOException {
        if (buf == null) {
            throw new NullPointerException(
                    lStrings.getString("err.io.nullArray"));
        }


        if (offset < 0 || len < 0 || offset+len > buf.length) {
            String msg = lStrings.getString("err.io.indexOutOfBounds");
            Object[] msgArgs = new Object[3];
            msgArgs[0] = Integer.valueOf(offset);
            msgArgs[1] = Integer.valueOf(len);
            msgArgs[2] = Integer.valueOf(buf.length);
            msg = MessageFormat.format(msg, msgArgs);
            throw new IndexOutOfBoundsException(msg);
        }
        contentLength += len;
    }
}