统一修改表单参数(表单提交的空字符串统一转null)

统一修改表单参数(表单提交的空字符串统一转null)

1.介绍:

我们业务中有时会遇到提交的表单中某个参数为空字符串,导致后台接受的为空字符串("")而不是我们理想中的null,会增加一些不必要的处理。本文介绍通过过滤器filter统一修改表单参数。

<form method="post" action="/post">
<input type="text" name="name" value="">
<input type="submit" value="提交">
</form>

2.实现

由于自带的request.getParameterMap()不可修改。因此我们需要自定义RequestWrapper。该RequestWrapper初始化时传入原request的参数,并对参数进行筛选,删除value为空字符串("")的参数。然后过滤器filter内把原request替换为自定义的RequestWrapper。

2.1 自定义RequestWrapper

    import xxxx.common.util.MapRemoveUtils;
    
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletRequestWrapper;
    import java.util.HashMap;
    import java.util.Map;
    
    public class ParameterRequestWrapper extends HttpServletRequestWrapper {
    
        private Map<String, String[]> params = new HashMap<String, String[]>();
    
        @SuppressWarnings("unchecked")
        public ParameterRequestWrapper(HttpServletRequest request) {
            // 将request交给父类,以便于调用对应方法的时候,将其输出,其实父亲类的实现方式和第一种new的方式类似
            super(request);
            //将参数表,赋予给当前的Map以便于持有request中的参数
    
            Map<String, String[]> map = new HashMap<>(request.getParameterMap());
            //删除空字符串参数
            map=MapUtils.filterEmptyParam(map);
            this.params.putAll(map);
        }
    
        @Override
        public String getParameter(String name) {//重写getParameter,代表参数从当前类中的map获取
            String[] values = params.get(name);
            if (values == null || values.length == 0) {
                return null;
            }
            return values[0];
        }
    
        @Override
        public String[] getParameterValues(String name) {//同上
            return params.get(name);
        }
    
        public void addAllParameters(Map<String, Object> otherParams) {//增加多个参数
            for (Map.Entry<String, Object> entry : otherParams.entrySet()) {
                addParameter(entry.getKey(), entry.getValue());
            }
        }
    
    
        public void addParameter(String name, Object value) {//增加参数
            if (value != null) {
                if (value instanceof String[]) {
                    params.put(name, (String[]) value);
                } else if (value instanceof String) {
                    params.put(name, new String[]{(String) value});
                } else {
                    params.put(name, new String[]{String.valueOf(value)});
                }
            }
        }
    
        @Override
        public Map<String, String[]> getParameterMap() {
            return this.params;
        }
    
    
    }

2.2 ParameterEmptyFilter

    import xxxx.ParameterRequestWrapper;
    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;
    import org.springframework.http.HttpMethod;
    
    import javax.servlet.*;
    import javax.servlet.http.HttpServletRequest;
    import java.io.IOException;
    
    public class ParameterEmptyFilter implements Filter {
    
    
        protected final Log logger = LogFactory.getLog(this.getClass());
    
        @Override
        public void init(FilterConfig filterConfig) throws ServletException {
    
        }
    
        @Override
        public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException, ServletException {
            String method = ((HttpServletRequest) request).getMethod();
            if (HttpMethod.POST.name().equals(method)) {
                ParameterRequestWrapper requestWrapper = new ParameterRequestWrapper((HttpServletRequest) request);
                filterChain.doFilter(requestWrapper, response);
                return;
            }
            filterChain.doFilter(request, response);
        }
    
        @Override
        public void destroy() {
    
        }
    
    }

2.3 MapUtils

RequestWrapper会用到,用于删除map中空key或空value。

        public class MapUtils {
            
            public static Map<String,Object> filterEmptyParam(Map<String,Object> param){
                Map<String,Object> result = new HashMap<>();
                param = Maps.filterValues(param, s -> s != null && (!(s instanceof String) || !((String) s).isEmpty()));
                result.putAll(param);
                return result;
            }
        }

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转载自www.cnblogs.com/huanghuizhou/p/9297939.html
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