spring boot 将空字符串转换为null，防止mybatis-plus根据实体类查询时候带上空字符串查询

 

MyStringArgumentResolver
 

package com.qy.config;

import org.springframework.core.MethodParameter;
import org.springframework.util.StringUtils;
import org.springframework.web.bind.annotation.ValueConstants;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver;

public class MyStringArgumentResolver extends AbstractNamedValueMethodArgumentResolver {

    @Override
    protected NamedValueInfo createNamedValueInfo(MethodParameter parameter) {
        return  new NamedValueInfo("", false, ValueConstants.DEFAULT_NONE);
    }

    @Override
    protected Object resolveName(String name, MethodParameter parameter, NativeWebRequest request) throws Exception {

        String[] param = request.getParameterValues(name);
        if(param==null){
            return null;
        }



        if(StringUtils.isEmpty(param[0])){
            return null;
        }


        return param[0];
    }

    @Override
    public boolean supportsParameter(MethodParameter parameter) {
        return parameter.getParameterType().equals(Object.class);
    }
}

ParameterRequestWrapper

package com.qy.config;


import com.alibaba.fastjson.JSON;
import org.apache.commons.io.IOUtils;
import org.apache.commons.lang.StringUtils;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;

import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

public class ParameterRequestWrapper extends HttpServletRequestWrapper {

    private Map params = new HashMap();

    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 requestMap = request.getParameterMap();
        this.params.putAll(requestMap);
        this.modifyParameterValues();
    }

    /**
     * 重写getInputStream方法  post类型的请求参数必须通过流才能获取到值
     */
    @Override
    public ServletInputStream getInputStream() throws IOException {
        //非json类型，直接返回
        if (!super.getHeader(HttpHeaders.CONTENT_TYPE).equalsIgnoreCase(MediaType.APPLICATION_JSON_VALUE)) {
            return super.getInputStream();
        }
        //为空，直接返回
        String json = IOUtils.toString(super.getInputStream(), "utf-8");
        if (StringUtils.isEmpty(json)) {
            return super.getInputStream();
        }
        Map map = JSON.parseObject(json);
        Set set = map.keySet();
        Iterator it = set.iterator();
        while (it.hasNext()) {
            String key = (String) it.next();
            Object values = map.get(key);
            if (values instanceof String) {
                values = ((String) values).trim();
                if(values.equals("")){
                    values = null;
                }
            }
            map.put(key, values);
        }
        ByteArrayInputStream bis = new ByteArrayInputStream(JSON.toJSONString(map).getBytes("utf-8"));
        return new MyServletInputStream(bis);
    }

    /**
     * 将parameter的值去除空格后重写回去
     */
    public void modifyParameterValues() {
        Set set = params.keySet();
        Iterator it = set.iterator();
        while (it.hasNext()) {
            String key = (String) it.next();
            String[] values = params.get(key);
            values[0] = values[0].trim();
            if(values[0].equals("")){
                params.put(key, null);
            }else{
                params.put(key, values);
            }
        }
    }

    /**
     * 重写getParameter 参数从当前类中的map获取
     */
    @Override
    public String getParameter(String name) {
        String[] values = params.get(name);
        if (values == null || values.length == 0) {
            return null;
        }
        return values[0];
    }

    /**
     * 重写getParameterValues
     */
    public String[] getParameterValues(String name) {//同上
        return params.get(name);
    }

    class MyServletInputStream extends ServletInputStream {
        private ByteArrayInputStream bis;

        public MyServletInputStream(ByteArrayInputStream bis) {
            this.bis = bis;
        }

        @Override
        public boolean isFinished() {
            return true;
        }

        @Override
        public boolean isReady() {
            return true;
        }

        @Override
        public void setReadListener(ReadListener listener) {

        }

        @Override
        public int read() throws IOException {
            return bis.read();
        }
    }
}

ParamsFilter

package com.qy.config;


import org.springframework.stereotype.Component;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;


@Component
@WebFilter(urlPatterns = "/**", filterName = "ParamsFilter",dispatcherTypes=DispatcherType.REQUEST)
public class ParamsFilter implements Filter {


@Override
public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)
throws IOException, ServletException {
    ParameterRequestWrapper parmsRequest = new ParameterRequestWrapper((HttpServletRequest) arg0);
    arg2.doFilter(parmsRequest, arg1);
}

@Override
public void destroy() {

}

@Override
public void init(FilterConfig arg0) throws ServletException {

}


}

参考原文:https://blog.csdn.net/sinat_21184471/article/details/81481088
在基础上修改了get时候为空字符串则赋值为null