org.springframework.web.servlet.HttpServletBean Maven / Gradle / Ivy
/*
* Copyright 2002-2018 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.web.servlet;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.Set;
import jakarta.servlet.ServletConfig;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServlet;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeansException;
import org.springframework.beans.MutablePropertyValues;
import org.springframework.beans.PropertyAccessorFactory;
import org.springframework.beans.PropertyValue;
import org.springframework.beans.PropertyValues;
import org.springframework.context.EnvironmentAware;
import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.core.env.Environment;
import org.springframework.core.env.EnvironmentCapable;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceEditor;
import org.springframework.core.io.ResourceLoader;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.util.StringUtils;
import org.springframework.web.context.support.ServletContextResourceLoader;
import org.springframework.web.context.support.StandardServletEnvironment;
/**
* Simple extension of {@link jakarta.servlet.http.HttpServlet} which treats
* its config parameters ({@code init-param} entries within the
* {@code servlet} tag in {@code web.xml}) as bean properties.
*
* A handy superclass for any type of servlet. Type conversion of config
* parameters is automatic, with the corresponding setter method getting
* invoked with the converted value. It is also possible for subclasses to
* specify required properties. Parameters without matching bean property
* setter will simply be ignored.
*
*
This servlet leaves request handling to subclasses, inheriting the default
* behavior of HttpServlet ({@code doGet}, {@code doPost}, etc).
*
*
This generic servlet base class has no dependency on the Spring
* {@link org.springframework.context.ApplicationContext} concept. Simple
* servlets usually don't load their own context but rather access service
* beans from the Spring root application context, accessible via the
* filter's {@link #getServletContext() ServletContext} (see
* {@link org.springframework.web.context.support.WebApplicationContextUtils}).
*
*
The {@link FrameworkServlet} class is a more specific servlet base
* class which loads its own application context. FrameworkServlet serves
* as direct base class of Spring's full-fledged {@link DispatcherServlet}.
*
* @author Rod Johnson
* @author Juergen Hoeller
* @see #addRequiredProperty
* @see #initServletBean
* @see #doGet
* @see #doPost
*/
@SuppressWarnings("serial")
public abstract class HttpServletBean extends HttpServlet implements EnvironmentCapable, EnvironmentAware {
/** Logger available to subclasses. */
protected final Log logger = LogFactory.getLog(getClass());
@Nullable
private ConfigurableEnvironment environment;
private final Set requiredProperties = new HashSet<>(4);
/**
* Subclasses can invoke this method to specify that this property
* (which must match a JavaBean property they expose) is mandatory,
* and must be supplied as a config parameter. This should be called
* from the constructor of a subclass.
* This method is only relevant in case of traditional initialization
* driven by a ServletConfig instance.
* @param property name of the required property
*/
protected final void addRequiredProperty(String property) {
this.requiredProperties.add(property);
}
/**
* Set the {@code Environment} that this servlet runs in.
*
Any environment set here overrides the {@link StandardServletEnvironment}
* provided by default.
* @throws IllegalArgumentException if environment is not assignable to
* {@code ConfigurableEnvironment}
*/
@Override
public void setEnvironment(Environment environment) {
Assert.isInstanceOf(ConfigurableEnvironment.class, environment, "ConfigurableEnvironment required");
this.environment = (ConfigurableEnvironment) environment;
}
/**
* Return the {@link Environment} associated with this servlet.
*
If none specified, a default environment will be initialized via
* {@link #createEnvironment()}.
*/
@Override
public ConfigurableEnvironment getEnvironment() {
if (this.environment == null) {
this.environment = createEnvironment();
}
return this.environment;
}
/**
* Create and return a new {@link StandardServletEnvironment}.
*
Subclasses may override this in order to configure the environment or
* specialize the environment type returned.
*/
protected ConfigurableEnvironment createEnvironment() {
return new StandardServletEnvironment();
}
/**
* Map config parameters onto bean properties of this servlet, and
* invoke subclass initialization.
* @throws ServletException if bean properties are invalid (or required
* properties are missing), or if subclass initialization fails.
*/
@Override
public final void init() throws ServletException {
// Set bean properties from init parameters.
PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
if (!pvs.isEmpty()) {
try {
BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
initBeanWrapper(bw);
bw.setPropertyValues(pvs, true);
}
catch (BeansException ex) {
if (logger.isErrorEnabled()) {
logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);
}
throw ex;
}
}
// Let subclasses do whatever initialization they like.
initServletBean();
}
/**
* Initialize the BeanWrapper for this HttpServletBean,
* possibly with custom editors.
*
This default implementation is empty.
* @param bw the BeanWrapper to initialize
* @throws BeansException if thrown by BeanWrapper methods
* @see org.springframework.beans.BeanWrapper#registerCustomEditor
*/
protected void initBeanWrapper(BeanWrapper bw) throws BeansException {
}
/**
* Subclasses may override this to perform custom initialization.
* All bean properties of this servlet will have been set before this
* method is invoked.
*
This default implementation is empty.
* @throws ServletException if subclass initialization fails
*/
protected void initServletBean() throws ServletException {
}
/**
* Overridden method that simply returns {@code null} when no
* ServletConfig set yet.
* @see #getServletConfig()
*/
@Override
@Nullable
public String getServletName() {
return (getServletConfig() != null ? getServletConfig().getServletName() : null);
}
/**
* PropertyValues implementation created from ServletConfig init parameters.
*/
private static class ServletConfigPropertyValues extends MutablePropertyValues {
/**
* Create new ServletConfigPropertyValues.
* @param config the ServletConfig we'll use to take PropertyValues from
* @param requiredProperties set of property names we need, where
* we can't accept default values
* @throws ServletException if any required properties are missing
*/
public ServletConfigPropertyValues(ServletConfig config, Set requiredProperties)
throws ServletException {
Set missingProps = (!CollectionUtils.isEmpty(requiredProperties) ?
new HashSet<>(requiredProperties) : null);
Enumeration paramNames = config.getInitParameterNames();
while (paramNames.hasMoreElements()) {
String property = paramNames.nextElement();
Object value = config.getInitParameter(property);
addPropertyValue(new PropertyValue(property, value));
if (missingProps != null) {
missingProps.remove(property);
}
}
// Fail if we are still missing properties.
if (!CollectionUtils.isEmpty(missingProps)) {
throw new ServletException(
"Initialization from ServletConfig for servlet '" + config.getServletName() +
"' failed; the following required properties were missing: " +
StringUtils.collectionToDelimitedString(missingProps, ", "));
}
}
}
}