Spring DataBinder throws StringIndexOutOfBoundsException for map property without nested property path

Since upgrading to Spring 6.2. we have the Issue that maps in form-data requests are no longer working. After switching the DTO to using String keys, we are now getting an IndexOutOfRange in DataVinder.createMap https://github.com/spring-projects/spring-framework/commit/e48cbc5ba8f631d448c8dbbf33b8c4d7ce420fdc#diff-1f22c41307a3ddcec8f1bc7a237d3b77ac7564883f4c663402993affac8a5756R1071

the issue seems to be the +2 in String nestedPath = name.substring(0, endIdx + 2); this works if the name is something like: mapname[91].myparam but not if the map is just key and value then having name mapname[91]

The tests for this method do not cover my case so I am wondering if this my usecase might no longer be supported?

Comment From: simonbasle

Hi @n0rthdev, can you provide a concrete example (ideally in the form of a simple unit test) of a map binding that used to work in 6.1 but doesn't in 6.2? I'm especially interested in the structure of the object you store as the map's value.

Comment From: n0rthdev

Hi @simonbasle, I will build a testcase. However, the issue we are facing is when the value isn't any custom object, but just a String. (might also be the case for any simple types) because then there is no nested path.

Comment From: n0rthdev

@simonbasle

Inside of DataBinderConstructTests

    @Test
    void mapStringBinding() {
        MapValueResolver valueResolver = new MapValueResolver(Map.of(
                "stringMap[a]", "value1",
                "stringMap[b]", "value2",
                "stringMap['c']", "value3"));

        DataBinder binder = initDataBinder(MapStringClass.class);
        binder.construct(valueResolver);

        MapStringClass stringClass = getTarget(binder);
        Map<String, String> map = stringClass.stringMap();

        assertThat(map).hasSize(3);
        assertThat(map.get("a")).isEqualTo("value1");
        assertThat(map.get("b")).isEqualTo("value2");
        assertThat(map.get("c")).isEqualTo("value3");
    }

    private record MapStringClass(Map<String, String> stringMap) {
    }

The stacktrace my test is producing.

begin 0, end 13, length 12
java.lang.StringIndexOutOfBoundsException: begin 0, end 13, length 12
    at java.base/java.lang.String.checkBoundsBeginEnd(String.java:4606)
    at java.base/java.lang.String.substring(String.java:2709)
    at org.springframework.validation.DataBinder.createMap(DataBinder.java:1083)
    at org.springframework.validation.DataBinder.createObject(DataBinder.java:964)
    at org.springframework.validation.DataBinder.construct(DataBinder.java:909)
    at org.springframework.validation.DataBinderConstructTests.mapStringBinding(DataBinderConstructTests.java:151)
    at java.base/java.lang.reflect.Method.invoke(Method.java:569)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)

Comment From: simonbasle

Yeah I understand how there could be a StringIndexOutOfBoundsException in 6.2, but this test also fails in 6.1 where the result Map contains null values.

Comment From: n0rthdev

Hmmmm. Our usecase was working in 6.1, However, we are not calling this directly so it might be that Spring 6.1 might have used different logic to parse our data structure. I can take a look if this is of value for you. Are you planning of implementing support for these kind of maps for the databinder or would you consider my testcase a use outside of the specification?

Comment From: simonbasle

@n0rthdev yeah if you can provide more insight / an example closer to your actual DTO structure that would be valuable. You also mentioned a change in the DTO to use string keys?

Feel free to also investigate the issue further as well. I'm not sure yet if your particular use case is within what's supposed to be supported.

Comment From: jochenchrist

Same issue here, this prevents us from upgrading to Spring Boot 3.4.0.

Here is a minimal example that runs with Spring Boot 3.3.5, but fails with Spring Boot 3.4.0:

package com.example.spring_web_key_value_demo

import org.junit.jupiter.api.Test
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc
import org.springframework.boot.test.context.SpringBootTest
import org.springframework.stereotype.Controller
import org.springframework.test.web.servlet.MockMvc
import org.springframework.test.web.servlet.post
import org.springframework.web.bind.annotation.ModelAttribute
import org.springframework.web.bind.annotation.PostMapping
import org.springframework.web.bind.annotation.ResponseBody

@SpringBootTest
@AutoConfigureMockMvc
class SpringWebKeyValueTests(
  @Autowired val mockMvc: MockMvc,
) {

  @Test
  fun postKeyValue() {
    mockMvc.post("/spring-web-key-value") {
      param("someMap[a]", "valueA")
    }.andExpect {
      status { isOk() }
      content { string("valueA") }
    }
  }

}


@Controller
class SpringWebKeyValueController {
  @PostMapping("/spring-web-key-value")
  @ResponseBody
  fun postKeyValue(@ModelAttribute("payload") payload: PayloadWithMap): String {
    println(payload)
    return payload.someMap.get("a")!!
  }
}

data class PayloadWithMap(
  val someMap: Map<String, String?> = mutableMapOf(),
)

Exception:

jakarta.servlet.ServletException: Request processing failed: java.lang.StringIndexOutOfBoundsException: Range [0, 11) out of bounds for length 10

    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1022)
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:914)
    at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:590)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:885)
    at org.springframework.test.web.servlet.TestDispatcherServlet.service(TestDispatcherServlet.java:72)
    at jakarta.servlet.http.HttpServlet.service(HttpServlet.java:658)
    at org.springframework.mock.web.MockFilterChain$ServletFilterProxy.doFilter(MockFilterChain.java:165)
    at org.springframework.mock.web.MockFilterChain.doFilter(MockFilterChain.java:132)
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
    at org.springframework.test.web.servlet.setup.MockMvcFilterDecorator.doFilter(MockMvcFilterDecorator.java:162)
    at org.springframework.mock.web.MockFilterChain.doFilter(MockFilterChain.java:132)
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
    at org.springframework.test.web.servlet.setup.MockMvcFilterDecorator.doFilter(MockMvcFilterDecorator.java:162)
    at org.springframework.mock.web.MockFilterChain.doFilter(MockFilterChain.java:132)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:116)
    at org.springframework.test.web.servlet.setup.MockMvcFilterDecorator.doFilter(MockMvcFilterDecorator.java:162)
    at org.springframework.mock.web.MockFilterChain.doFilter(MockFilterChain.java:132)
    at org.springframework.test.web.servlet.MockMvc.perform(MockMvc.java:201)
    at org.springframework.test.web.servlet.MockHttpServletRequestDsl.perform$spring_test(MockHttpServletRequestDsl.kt:222)
    at org.springframework.test.web.servlet.MockMvcExtensionsKt.post(MockMvcExtensions.kt:56)
    at com.example.spring_web_key_value_demo.SpringWebKeyValueTests.postKeyValue(SpringWebKeyValueTests.kt:24)
    at java.base/java.lang.reflect.Method.invoke(Method.java:580)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1596)
Caused by: java.lang.StringIndexOutOfBoundsException: Range [0, 11) out of bounds for length 10
    at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:55)
    at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:52)
    at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:213)
    at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:210)
    at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:98)
    at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckFromToIndex(Preconditions.java:112)
    at java.base/jdk.internal.util.Preconditions.checkFromToIndex(Preconditions.java:349)
    at java.base/java.lang.String.checkBoundsBeginEnd(String.java:4865)
    at java.base/java.lang.String.substring(String.java:2834)
    at org.springframework.validation.DataBinder.createMap(DataBinder.java:1083)
    at org.springframework.validation.DataBinder.createObject(DataBinder.java:964)
    at org.springframework.validation.DataBinder.construct(DataBinder.java:909)
    at org.springframework.web.bind.ServletRequestDataBinder.construct(ServletRequestDataBinder.java:116)
    at org.springframework.web.servlet.mvc.method.annotation.ServletModelAttributeMethodProcessor.constructAttribute(ServletModelAttributeMethodProcessor.java:157)
    at org.springframework.web.method.annotation.ModelAttributeMethodProcessor.resolveArgument(ModelAttributeMethodProcessor.java:148)
    at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:122)
    at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:224)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:178)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:118)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:986)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:891)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1088)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:978)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014)

Comment From: sbrannen

Thanks for the reproducer, @jochenchrist.

I converted that from Kotlin to Java as follows.

import java.util.Map;

import example.SpringWebKeyValueTests.SpringWebKeyValueController;
import org.junit.jupiter.api.Test;

import org.springframework.test.context.junit.jupiter.web.SpringJUnitWebConfig;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.context.WebApplicationContext;

import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
import static org.springframework.test.web.servlet.setup.MockMvcBuilders.webAppContextSetup;

@SpringJUnitWebConfig(SpringWebKeyValueController.class)
class SpringWebKeyValueTests {

    @Test
    void postKeyValue(WebApplicationContext wac) throws Exception {
        MockMvc mockMvc = webAppContextSetup(wac).build();
        mockMvc.perform(post("/spring-web-key-value").param("someMap[a]", "valueA"))
            .andExpect(status().isOk())
            .andExpect(content().string("valueA"));
    }

    record PayloadWithMap(Map<String, String> someMap) {}

    @RestController
    static class SpringWebKeyValueController {

        @PostMapping("/spring-web-key-value")
        String postKeyValue(@ModelAttribute("payload") PayloadWithMap payload) {
            return payload.someMap.get("a");
        }
    }

}

In DataBinder.createMap(...), if I replace:

String nestedPath = name.substring(0, endIdx + 2);

... with:

String nestedPath = ((name.length() > endIdx + 1) ? name.substring(0, endIdx + 2) : "");

... that allows SpringWebKeyValueTests to pass.

I have not verified if this is the ideal solution, but the team will look into it.

Comment From: sbrannen

This is closely related to:

34121

And the two should be looked at in conjunction.

Spring DataBinder throws StringIndexOutOfBoundsException for map property without nested property path

34121