我使用 javax.servlet.http.HttpServletRequest 来实现Web应用程序。
使用 getParameter 方法获取请求的参数没有问题。但是我不知道如何在我的请求中设置参数。
答案 0 :(得分:29)
您不能,不使用标准API。 HttpServletRequest
表示服务器收到的请求,因此添加新参数不是有效选项(就API而言)。
原则上你可以实现一个包含原始请求的HttpServletRequestWrapper
的子类,并拦截getParameter()
方法,并在你转发时传递包装的请求。
如果你选择这条路线,你应该使用Filter
将HttpServletRequest
替换为HttpServletRequestWrapper
:
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
if (servletRequest instanceof HttpServletRequest) {
HttpServletRequest request = (HttpServletRequest) servletRequest;
// Check wether the current request needs to be able to support the body to be read multiple times
if (MULTI_READ_HTTP_METHODS.contains(request.getMethod())) {
// Override current HttpServletRequest with custom implementation
filterChain.doFilter(new HttpServletRequestWrapper(request), servletResponse);
return;
}
}
filterChain.doFilter(servletRequest, servletResponse);
}
答案 1 :(得分:20)
如果你真的想这样做,请创建一个HttpServletRequestWrapper。
public class AddableHttpRequest extends HttpServletRequestWrapper {
private HashMap params = new HashMap();
public AddableingHttpRequest(HttpServletRequest request) {
super(request);
}
public String getParameter(String name) {
// if we added one, return that one
if ( params.get( name ) != null ) {
return params.get( name );
}
// otherwise return what's in the original request
HttpServletRequest req = (HttpServletRequest) super.getRequest();
return validate( name, req.getParameter( name ) );
}
public void addParameter( String name, String value ) {
params.put( name, value );
}
}
答案 2 :(得分:15)
从你的问题来看,我认为你要做的是存储一些东西(一个对象,一个字符串......)然后使用RequestDispatcher()将它转移到另一个servlet。 要做到这一点,您不需要使用
设置参数,而是设置属性void setAttribute(String name, Object o);
然后
Object getAttribute(String name);
答案 3 :(得分:1)
如前所述,使用HttpServletReqiestWrapper是可行的方法,但是这些帖子中遗漏的部分是除了覆盖方法getParameter()之外,还应该覆盖其他参数相关的方法以产生一致的响应。例如自定义请求包装器添加的param的值也应包含在方法getParameterMap()返回的参数映射中。这是一个例子:
public class AddableHttpRequest extends HttpServletRequestWrapper {
/** A map containing additional request params this wrapper adds to the wrapped request */
private final Map<String, String> params = new HashMap<>();
/**
* Constructs a request object wrapping the given request.
* @throws java.lang.IllegalArgumentException if the request is null
*/
AddableHttpRequest(final HttpServletRequest request) {
super(request)
}
@Override
public String getParameter(final String name) {
// if we added one with the given name, return that one
if ( params.get( name ) != null ) {
return params.get( name );
} else {
// otherwise return what's in the original request
return super.getParameter(name);
}
}
/**
* *** OVERRIDE THE METHODS BELOW TO REFLECT PARAMETERS ADDED BY THIS WRAPPER ****
*/
@Override
public Map<String, String> getParameterMap() {
// defaulf impl, should be overridden for an approprivate map of request params
return super.getParameterMap();
}
@Override
public Enumeration<String> getParameterNames() {
// defaulf impl, should be overridden for an approprivate map of request params names
return super.getParameterNames();
}
@Override
public String[] getParameterValues(final String name) {
// defaulf impl, should be overridden for an approprivate map of request params values
return super.getParameterValues(name);
}
}
答案 4 :(得分:1)
最受支持的解决方案通常可以使用,但是对于Spring和/或Spring Boot,除非专门实现了@RequestParam
,否则这些值将不会连接到以getParameterValues()
注释的控制器方法中的参数。我在这里和this blog中合并了解决方案:
import java.util.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
public class MutableHttpRequest extends HttpServletRequestWrapper {
private final Map<String, String[]> mutableParams = new HashMap<>();
public MutableHttpRequest(final HttpServletRequest request) {
super(request);
}
public MutableHttpRequest addParameter(String name, String value) {
if (value != null)
mutableParams.put(name, new String[] { value });
return this;
}
@Override
public String getParameter(final String name) {
String[] values = getParameterMap().get(name);
return Arrays.stream(values)
.findFirst()
.orElse(super.getParameter(name));
}
@Override
public Map<String, String[]> getParameterMap() {
Map<String, String[]> allParameters = new HashMap<>();
allParameters.putAll(super.getParameterMap());
allParameters.putAll(mutableParams);
return Collections.unmodifiableMap(allParameters);
}
@Override
public Enumeration<String> getParameterNames() {
return Collections.enumeration(getParameterMap().keySet());
}
@Override
public String[] getParameterValues(final String name) {
return getParameterMap().get(name);
}
}
请注意,此代码不是超级优化的,但它可以工作。
答案 5 :(得分:0)
缺少的getParameterMap覆盖最终成为我的实际问题。所以这就是我最终得到的:
import java.util.HashMap;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
/***
* Request wrapper enabling the update of a request-parameter.
*
* @author E.K. de Lang
*
*/
final class HttpServletRequestReplaceParameterWrapper
extends HttpServletRequestWrapper
{
private final Map<String, String[]> keyValues;
@SuppressWarnings("unchecked")
HttpServletRequestReplaceParameterWrapper(HttpServletRequest request, String key, String value)
{
super(request);
keyValues = new HashMap<String, String[]>();
keyValues.putAll(request.getParameterMap());
// Can override the values in the request
keyValues.put(key, new String[] { value });
}
@SuppressWarnings("unchecked")
HttpServletRequestReplaceParameterWrapper(HttpServletRequest request, Map<String, String> additionalRequestParameters)
{
super(request);
keyValues = new HashMap<String, String[]>();
keyValues.putAll(request.getParameterMap());
for (Map.Entry<String, String> entry : additionalRequestParameters.entrySet()) {
keyValues.put(entry.getKey(), new String[] { entry.getValue() });
}
}
@Override
public String getParameter(String name)
{
if (keyValues.containsKey(name)) {
String[] strings = keyValues.get(name);
if (strings == null || strings.length == 0) {
return null;
}
else {
return strings[0];
}
}
else {
// Just in case the request has some tricks of it's own.
return super.getParameter(name);
}
}
@Override
public String[] getParameterValues(String name)
{
String[] value = this.keyValues.get(name);
if (value == null) {
// Just in case the request has some tricks of it's own.
return super.getParameterValues(name);
}
else {
return value;
}
}
@Override
public Map<String, String[]> getParameterMap()
{
return this.keyValues;
}
}
答案 6 :(得分:-4)
抱歉,为什么不使用以下结构:
request.getParameterMap().put(parameterName, new String[] {parameterValue});