Spring多次读取HttpServletRequest

素颜马尾好姑娘i 2022-11-13 11:25 295阅读 0赞

# 1.介绍 #

如何使用Spring多次从HttpServletRequest读取正文。

HttpServletRequest是一个接口，该接口公开getInputStream()方法以读取正文。 默认情况下，此InputStream中的数据只能读取一次。

# 2. Maven 依赖 #

<dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-webmvc</artifactId>
        <version>5.2.0.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>4.0.1</version>
    </dependency>

另外，由于我们使用的是application/json内容类型，因此需要jackson-databind依赖项：

<dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.10.0</version>
    </dependency>

# 3.Spring的ContentCachingRequestWrapper #

Spring提供了一个ContentCachingRequestWrapper类。 此类提供一种方法getContentAsByteArray()来多次读取正文。

但是，此类有一个局限性：无法使用getInputStream()和getReader()方法多次读取正文。

**此类通过使用InputStream来缓存请求正文。 如果在其中一个过滤器中读取InputStream，则过滤器链中的其他后续过滤器将无法再读取它。** 由于存在此限制，因此此类不适用于所有情况。

为了克服此限制，现在让我们看一个更通用的解决方案。

# 4.扩展HttpServletRequest #

让创建一个新类CachedBodyHttpServletRequest，它扩展了HttpServletRequestWrapper。 这样，我们不需要重写HttpServletRequest接口的所有抽象方法。

HttpServletRequestWrapper类具有两个抽象方法getInputStream()和getReader()。 将覆盖这两个方法，并创建一个新的构造函数。

## 4.1构造函数 ##

首先，创建一个构造函数。 在其中，将从实际的InputStream中读取正文并将其存储在byte \[\]对象中：

public class CachedBodyHttpServletRequest extends HttpServletRequestWrapper { 
    
        private byte[] cachedBody;
    
        public CachedBodyHttpServletRequest(HttpServletRequest request) throws IOException { 
            super(request);
            InputStream requestInputStream = request.getInputStream();
            this.cachedBody = StreamUtils.copyToByteArray(requestInputStream);
        }
    }

结果，将能够多次读取正文。

## 4.2getInputStream() ##

接下来，重写getInputStream()方法。 将使用此方法读取原始主体并将其转换为对象。

在此方法中，将创建并返回CachedBodyServletInputStream类的新对象（ServletInputStream的实现）：

@Override
    public ServletInputStream getInputStream() throws IOException { 
        return new CachedBodyServletInputStream(this.cachedBody);
    }

## 4.3. getReader() ##

@Override
    public BufferedReader getReader() throws IOException { 
        ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(this.cachedBody);
        return new BufferedReader(new InputStreamReader(byteArrayInputStream));
    }

# 5.ServletInputStream的实现 #

创建一个类-CachedBodyServletInputStream-该类将实现ServletInputStream。 在此类中，将创建一个新的构造函数，并覆盖isFinished()，isReady()和read()方法。

## 5.1构造函数 ##

在其中，将使用该字节数组创建一个新的ByteArrayInputStream实例。 之后，将其分配给全局变量cachedBodyInputStream：

public class CachedBodyServletInputStream extends ServletInputStream { 
    
        private InputStream cachedBodyInputStream;
    
        public CachedBodyServletInputStream(byte[] cachedBody) { 
            this.cachedBodyInputStream = new ByteArrayInputStream(cachedBody);
        }
    }

## 5.2. read() ##

覆盖read()方法。 在此方法中，调用ByteArrayInputStream＃read：

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

### 5.3. isFinished() ###

覆盖isFinished()方法。 此方法指示InputStream是否有更多数据要读取。 当零字节可读取时，它返回true：

@Override
    public boolean isFinished() { 
        return cachedBody.available() == 0;
    }

## 5.4. isReady() ##

覆盖isReady()方法。 此方法指示InputStream是否已准备好读取。

由于已经将InputStream复制到字节数组中，因此将返回true指示其始终可用：

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

# 6.完整代码 #

import java.io.BufferedReader;
    import java.io.ByteArrayInputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.InputStreamReader;
    
    import javax.servlet.ServletInputStream;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletRequestWrapper;
    
    import org.springframework.util.StreamUtils;
    /** * @author Created by niugang on 2021-03-26 14:02 */
    public class CachedBodyHttpServletRequest extends HttpServletRequestWrapper { 
    
        private byte[] cachedBody;
    
        public CachedBodyHttpServletRequest(HttpServletRequest request) throws IOException { 
            super(request);
            InputStream requestInputStream = request.getInputStream();
            this.cachedBody = StreamUtils.copyToByteArray(requestInputStream);
        }
    
        @Override
        public ServletInputStream getInputStream() throws IOException { 
            return new CachedBodyServletInputStream(this.cachedBody);
        }
    
        @Override
        public BufferedReader getReader() throws IOException { 
      
            ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(this.cachedBody);
            return new BufferedReader(new InputStreamReader(byteArrayInputStream));
        }
    }

import java.io.ByteArrayInputStream;
    import java.io.IOException;
    import java.io.InputStream;
    
    import javax.servlet.ReadListener;
    import javax.servlet.ServletInputStream;
    /** * @author Created by niugang on 2021-03-26 14:02 */
    public class CachedBodyServletInputStream extends ServletInputStream { 
    
        private InputStream cachedBodyInputStream;
    
        public CachedBodyServletInputStream(byte[] cachedBody) { 
            this.cachedBodyInputStream = new ByteArrayInputStream(cachedBody);
        }
    
        @Override
        public boolean isFinished() { 
            try { 
                return cachedBodyInputStream.available() == 0;
            } catch (IOException e) { 
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            return false;
        }
    
        @Override
        public boolean isReady() { 
            return true;
        }
    
        @Override
        public void setReadListener(ReadListener readListener) { 
            throw new UnsupportedOperationException();
        }
    
        @Override
        public int read() throws IOException { 
            return cachedBodyInputStream.read();
        }
    }

# 7.过滤器 #

最后，创建一个新的过滤器以使用CachedBodyHttpServletRequest类。扩展Spring的OncePerRequestFilter类。 此类具有抽象方法doFilterInternal()。

在此方法中，将从实际的请求对象创建CachedBodyHttpServletRequest类的对象：

然后，将这个新的请求包装对象传递给过滤器链。 因此，对getInputStream（）方法的所有后续调用都将调用重写的方法：

import javax.servlet.FilterChain;
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebFilter;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import com.example.demo.cacherequest.CachedBodyHttpServletRequest;
    import org.springframework.core.Ordered;
    import org.springframework.core.annotation.Order;
    import org.springframework.stereotype.Component;
    import org.springframework.web.filter.OncePerRequestFilter;
    /** * @author Created by niugang on 2021-03-26 14:03 */
    @Order(value = Ordered.HIGHEST_PRECEDENCE)
    @Component
    @WebFilter(filterName = "ContentCachingFilter", urlPatterns = "/*")
    public class ContentCachingFilter extends OncePerRequestFilter { 
    
        @Override
        protected void doFilterInternal(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, FilterChain filterChain) throws ServletException, IOException { 
            System.out.println("IN ContentCachingFilter ");
            //请求包装
            CachedBodyHttpServletRequest cachedBodyHttpServletRequest = new CachedBodyHttpServletRequest(httpServletRequest);
            filterChain.doFilter(cachedBodyHttpServletRequest, httpServletResponse);
        }

在新建一个过滤器尝试从请求中，获取请求内容

import java.io.IOException;
    import java.io.InputStream;
    
    import javax.servlet.FilterChain;
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebFilter;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import org.springframework.core.Ordered;
    import org.springframework.core.annotation.Order;
    import org.springframework.stereotype.Component;
    import org.springframework.util.StreamUtils;
    import org.springframework.web.filter.OncePerRequestFilter;
    /** * @author Created by niugang on 2021-03-26 14:06 */
    @Order(Ordered.LOWEST_PRECEDENCE)
    @Component
    @WebFilter(filterName = "printRequestContentFilter", urlPatterns = "/*")
    public class PrintRequestContentFilter extends OncePerRequestFilter { 
        @Override
        protected void doFilterInternal(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, FilterChain filterChain) throws ServletException, IOException { 
            System.out.println("IN PrintRequestContentFilter ");
            InputStream inputStream = httpServletRequest.getInputStream();
            byte[] body = StreamUtils.copyToByteArray(inputStream);
            System.out.println("In PrintRequestContentFilter. Request body is: " + new String(body));
            filterChain.doFilter(httpServletRequest, httpServletResponse);
        }
    }

# 8.测试 #

@Data
    public class Person { 
        private String firstName;
    
        private String lastName;
    
        private int age;
    }

@RestController
    public class PersonController { 
    
        @PostMapping(value = "/person")
        @ResponseStatus(value = HttpStatus.NO_CONTENT)
        public void printPerson(@RequestBody Person person) { 
    
            System.out.println("In Demo Controller. Person " + "is : " + person);
        }
    
        @GetMapping(value = "/person")
        @ResponseStatus(value = HttpStatus.NO_CONTENT)
        public void getPerson() { 
    
            System.out.println("In Demo Controller get method.");
        }
    }

> 请求post person 输出如下内容
> 
> IN ContentCachingFilter  
> IN PrintRequestContentFilter  
> In PrintRequestContentFilter. Request body is: \{  
> “firstName”:“xxxx”,  
> “lastName”:“aaaa”,  
> “age”:15  
> \}  
> In Demo Controller. Person is : Person(firstName=xxxx, lastName=aaaa, age=15)

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