PostReplaceFilter.java

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package com.sun.jersey.api.container.filter;

import com.sun.jersey.api.core.ResourceConfig;
import com.sun.jersey.api.representation.Form;
import com.sun.jersey.core.header.MediaTypes;
import com.sun.jersey.spi.container.ContainerRequest;
import com.sun.jersey.spi.container.ContainerRequestFilter;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.Response.Status;
import javax.ws.rs.core.UriBuilder;

/**
 * A filter to support HTTP method replacing of a POST request to a request
 * utilizing another HTTP method for the case where proxies or HTTP
 * servers would otherwise block that HTTP method.
 * <p>
 * This filter may be used to replace a POST request with a PUT, DELETE or GET
 * request.
 * <p>
 * Replacement will occur if the request method is POST and there exists either
 * a request header "X-HTTP-Method-Override", or
 * a query parameter "_method" with a non-empty value. That value
 * will be the HTTP method that replaces the POST method. In addition to that,
 * when replacing the POST method with GET, the filter will convert the form parameters
 * to query parameters. If the filter is configured to look for both the X-HTTP-Method-Override
 * header as well as the _method query parameter (the default setting), both are present in the
 * request and they differ, the filter returns {@link Status#BAD_REQUEST} response.
 * <p>
 * When an application is deployed as a Servlet or Filter this Jersey filter can be
 * registered using the following initialization parameter:
 * <blockquote><pre>
 *     <init-param>
 *         <param-name>com.sun.jersey.spi.container.ContainerRequestFilters</param-name>
 *         <param-value>com.sun.jersey.api.container.filter.PostReplaceFilter</param-value>
 *     </init-param>
 * </pre></blockquote>
 * <p>
 * The filter can be configured using the com.sun.jersey.api.container.filter.PostReplaceFilterConfig property.
 * See {@link #PROPERTY_POST_REPLACE_FILTER_CONFIG} for the supported property values.
 *
 * @author Paul.Sandoz@Sun.Com
 * @author Martin Matula
 * @author Fredy Nagy
 * @author Florian Hars (florian@hars.de)
 *
 * @see com.sun.jersey.api.container.filter
 */
public class PostReplaceFilter implements ContainerRequestFilter {

    /**
     * Property that may contain a comma-separated list of the configuration flags to be set on this filter. {@link ConfigFlag} enum lists the allowed config flags.
     * If this property is not set, the default value "HEADER,QUERY" will be used to initialize the filter.
     * <p>
     * When an application is deployed as a servlet or filter this property can be set using the following initialization parameter:
     * <blockquote><pre>
     *     <init-param>
     *         <param-name>com.sun.jersey.api.container.filter.PostReplaceFilterConfig</param-name>
     *         <param-value>HEADER</param-value>
     *     </init-param>
     * </pre></blockquote>
     * The above setting would cause the filter would only look at the X-HTTP-Method-Override header and ignore _method query parameter.
     */
    public static final String PROPERTY_POST_REPLACE_FILTER_CONFIG = "com.sun.jersey.api.container.filter.PostReplaceFilterConfig";

    private final int config;

    /**
     * Enum representing configuration flags that can be set on the filter. Each literal of this enum is a flag that can either be turned on (included in the config) or not.
     */
    public enum ConfigFlag {

        /** If added to the config, causes the filter to look for a method override in the X-HTTP-Method-Override header */
        HEADER(1),
        /** If added to the config, causes the filter to look for a method override in the _method query parameter */
        QUERY(2);
        private final int flag;

        private ConfigFlag(int flag) {
            this.flag = flag;
        }

        /**
         * Returns the numeric value of the bit corresponding to this flag.
         * @return numeric value of this flag
         */
        public int getFlag() {
            return flag;
        }

        /**
         * Returns true if the bit corresponding to this flag is set in a given integer value
         * @param config Integer value to check for the bit corresponding to this flag
         * @return true if the passed value has the bit corresponding to this flag set
         */
        public boolean isPresentIn(int config) {
            return (config & flag) == flag;
        }
    }

    /**
     * Initializes this filter with {@link #PROPERTY_POST_REPLACE_FILTER_CONFIG} property value from the application resource config.
     * If the property has no value, both {@link ConfigFlag#HEADER} and {@link ConfigFlag#QUERY} will be added to the config.
     *
     * @param rc resource config (injected by Jersey)
     */
    public PostReplaceFilter(@Context ResourceConfig rc) {
        this(configStringToConfig((String) rc.getProperty(PROPERTY_POST_REPLACE_FILTER_CONFIG)));
    }

    /**
     * Initializes this filter with config flags.
     * @param configFlags Config flags to initialize the filter with. If no config flags are passed,
     * both {@link ConfigFlag#HEADER} and {@link ConfigFlag#QUERY} will be added to the config.
     */
    public PostReplaceFilter(ConfigFlag... configFlags) {
        int c = 0;
        for (ConfigFlag cf : configFlags) {
            c |= cf.getFlag();
        }
        if (c == 0) {
            c = 3;
        }
        this.config = c;
    }

    /**
     * Converts a config string (from the init parameters) to an array of config flags.
     *
     * @param configString config string
     * @return array of ConfigFlag objects
     */
    private static ConfigFlag[] configStringToConfig(String configString) {
        if (configString == null) {
            return new ConfigFlag[0];
        }

        String[] parts = configString.toUpperCase().split(",");
        ArrayList<ConfigFlag> result = new ArrayList<ConfigFlag>(parts.length);
        for (String part : parts) {
            part = part.trim();
            if (part.length() > 0) {
                try {
                    result.add(ConfigFlag.valueOf(part));
                } catch (IllegalArgumentException e) {
                    Logger.getLogger(PostReplaceFilter.class.getName()).log(Level.WARNING, "Invalid config flag for " + PROPERTY_POST_REPLACE_FILTER_CONFIG + " property: {0}", part.trim());
                }
            }
        }
        return result.toArray(new ConfigFlag[result.size()]);
    }

    /**
     * Returns parameter value in a normalized form (uppercase, trimmed and null if empty string) considering the config flags.
     *
     * @param configFlag Config flag to look for (if set in the config, this method returns the param value, if not set, this method returns null).
     * @param paramsMap Map to retrieve the parameter from.
     * @param paramName Name of the parameter to retrieve.
     * @return Normalized parameter value. Never returns an empty string - converts it to null.
     */
    private String getParamValue(ConfigFlag configFlag, MultivaluedMap<String, String> paramsMap, String paramName) {
        String value = configFlag.isPresentIn(config) ? paramsMap.getFirst(paramName) : null;
        if (value == null) {
            return null;
        }
        value = value.trim();
        return value.length() == 0 ? null : value.toUpperCase();
    }

    @Override
    public ContainerRequest filter(ContainerRequest request) {
        if (!request.getMethod().equalsIgnoreCase("POST")) {
            return request;
        }

        String header = getParamValue(ConfigFlag.HEADER, request.getRequestHeaders(), "X-HTTP-Method-Override");
        String query = getParamValue(ConfigFlag.QUERY, request.getQueryParameters(), "_method");

        String override;
        if (header == null) {
            override = query;
        } else {
            override = header;
            if (query != null && !query.equals(header)) {
                throw new WebApplicationException(Response.status(Status.BAD_REQUEST).type(MediaType.TEXT_PLAIN).entity("Inconsistent POST override.\nX-HTTP-Method-Override: " + header + "\n_method: " + query).build());
            }
        }
        if (override == null) {
            return request;
        }
        request.setMethod(override);
        if (override.equals("GET")) {
            if (MediaTypes.typeEquals(MediaType.APPLICATION_FORM_URLENCODED_TYPE, request.getMediaType())) {
                UriBuilder ub = request.getRequestUriBuilder();
                Form f = request.getFormParameters();
                for (Map.Entry<String, List<String>> param : f.entrySet()) {
                    ub.queryParam(param.getKey(), param.getValue().toArray());
                }
                request.setUris(request.getBaseUri(), ub.build());
            }
        }
        return request;
    }
}