jpa,两个相互用@ManyToMany的实体，读取其中一个，就保存no session

Question

User实体

    @ManyToMany(targetEntity = Role.class, fetch = FetchType.EAGER)
    @JoinTable(name = "USER_ROLE_RELATION", joinColumns = @JoinColumn(name = "userId"), inverseJoinColumns = @JoinColumn(name = "roleId"))
    public Set<Role> getRoles() {

        return roles;
    }

Role实体：

    @ManyToMany(targetEntity = User.class,mappedBy = "roles")
    public Set<User> getUsers() {
        return users;
    }

当读取 User的时候，就报错：

    @Transactional(readOnly = true)
    @Override
    public Page<User> loadAllUser(Integer pageNo) {

        PageRequest request = new PageRequest(pageNo - 1, 10);

        return userRepository.findAll(request);
    }

HTTP Status 500 - Could not write content: failed to lazily initialize a collection of role: domain.Role.users, could not initialize proxy - no Session (through reference chain: domain.Response["data"]->org.springframework.data.domain.PageImpl["content"]->java.util.UnmodifiableRandomAccessList[0]->domain.User["roles"]->org.hibernate.collection.internal.PersistentSet[0]->domain.Role["users"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: failed to lazily initialize a collection of role: domain.Role.users, could not initialize proxy - no Session (through reference chain: domain.Response["data"]->org.springframework.data.domain.PageImpl["content"]->java.util.UnmodifiableRandomAccessList[0]->domain.User["roles"]->org.hibernate.collection.internal.PersistentSet[0]->domain.Role["users"])

怎么办？